Physics of the ether

Google

This is a digital copy of a book that was preserved for generations on library shelves before it was carefully scanned by Google as part of a project

to make the world's books discoverable online.

It has survived long enough for the copyright to expire and the book to enter the public domain. A public domain book is one that was never subject

to copyright or whose legal copyright term has expired. Whether a book is in the public domain may vary country to country. Public domain books

are our gateways to the past, representing a wealth of history, culture and knowledge that's often difficult to discover.

Marks, notations and other maiginalia present in the original volume will appear in this file - a reminder of this book's long journey from the

publisher to a library and finally to you.

Usage guidelines

Google is proud to partner with libraries to digitize public domain materials and make them widely accessible. Public domain books belong to the
public and we are merely their custodians. Nevertheless, this work is expensive, so in order to keep providing tliis resource, we liave taken steps to
prevent abuse by commercial parties, including placing technical restrictions on automated querying.
We also ask that you:

+ Make non-commercial use of the files We designed Google Book Search for use by individuals, and we request that you use these files for
personal, non-commercial purposes.

+ Refrain fivm automated querying Do not send automated queries of any sort to Google's system: If you are conducting research on machine
translation, optical character recognition or other areas where access to a large amount of text is helpful, please contact us. We encourage the
use of public domain materials for these purposes and may be able to help.

+ Maintain attributionTht GoogXt "watermark" you see on each file is essential for in forming people about this project and helping them find
additional materials through Google Book Search. Please do not remove it.

+ Keep it legal Whatever your use, remember that you are responsible for ensuring that what you are doing is legal. Do not assume that just
because we believe a book is in the public domain for users in the United States, that the work is also in the public domain for users in other
countries. Whether a book is still in copyright varies from country to country, and we can't offer guidance on whether any specific use of
any specific book is allowed. Please do not assume that a book's appearance in Google Book Search means it can be used in any manner
anywhere in the world. Copyright infringement liabili^ can be quite severe.

About Google Book Search

Google's mission is to organize the world's information and to make it universally accessible and useful. Google Book Search helps readers
discover the world's books while helping authors and publishers reach new audiences. You can search through the full text of this book on the web

at |http: //books .google .com/I

IimA^ C-tywh

• hrUei.

-aS/^^-^

*>

PHYSICS

OF THE

ETHEE

BY

S. TOLVER PRESTON.

LONDON:
E. & F. N. SPON, 48, CHAEING CROSS.

NEW YORK:
446, BBOOMB STEEET.

1875.

{All Bights reserved,)

/f P . e , 101

NOTICE.

SmoB this work was pablished in 1875, Ae Bubjeot has been developed
considerably further by me, as the following Ust of papers (selected
from a number) may serve to indicate.

(1^ Fhilosophical Magazine, Sept and Nov. 1877, Feb. 1878. — Papers
applying the constitution of the ether (as set forth in this book) to the
explanation of gravitation, by which all t^e complex postulates of Le Sage's
well-known theory may be removed — ^retaining only his simple fundamental
idea. The third of the above papers includes a reply to a criticism by
Dr. James Croll, F.R.S., on the subject of the previous two. [An Abstract
of these papers is given in Wiedmam,rik8 Annalen (JBeM.) Bd. Ill, 1879, page 729.]

(2) Nature, Jan. 15th, 1880. — " On a Mode of explaining the Transverse
Vibrations of Light." — ^A paper applying the above view of the constitution
of the ether as a possible means of accounting mechanically for the transverse
nature of light impulses, using here, as a supplementary aid, a suggestion thrown
out by the late Prof. Clerk Maxwell in his notice of the author s theory of the
ether, given in the EncyclopsBdia Brit., 1878, under article " iEther."

(3) Nature, March 20th, 1879, and Philosophical Magazine, Aug. 1879, and
Nov. 1880 — " On the Possibility of accounting for the continuance of Recurring
Changes in the Universe consistent with the Tendency to Temperature
Equifibrium." — Three papers applying the above hinetio theory of the ether
(as a natural sequence) to the movements of the larger seals stellar masses of the
universe immersed in the ether, with the view to suggest an explanation of the
possibility of the continuance of change in the universe consistent with the
prevalence of a general equilibrium of temperature or energy when sufficiently
large areas are taken into account — on the same principle as we know that a
(compound) gas can be in equilibrium of temperature as a whole, and yet
within areas which may be a considerable multiple (^ the mean path of the
molecules, the greatest diversity of temperature (and even of constitution) may
exist. [An Abstract of these papers is given by M. Violle, Memb. Inst, in the
Journal de Physique, Feb. 1880. It may be remarked that Dr. Croll (Phil,
Mag., May 1868, and July 1878) and Mr. Johnstone Stoney, F.R.S. {Proc, of the
Royal Society, 1868-69) have published papers which may be regarded as at
least a step in favour of the final conclusion of the author, which was arrived at
before be had seen these papers.]

(4) Philosophical Magazine, June 1877. — A paper applying thj kinetic
constitution of a gas to a conception of the mechanical mode of propagation
of sound in air, and an investigation of the conditions which must determine its
velocity under these premises. [A mathematical expression for the velocity, on
this basis, is appended to the paper in question by the late Prof. Clerk Maxwell —
an abstract of which may be found |q tl^e Journal de Physique, July 1878,
page 233.]

(6) Nature, March 17th, 1881. — " On some Points Relating to the Dynamics
of Radiant Matter '* — a paper connecting- some important discoveries of Mr. Crookes
with the view of the radiant constitution of the ether entertained by the author.

(6) Philosophical Magazine, May 1880. — " On Method in Causal Research,"
Philosophical Magazine, Jan. and March, 1881 ; papers on *' Action at a Distaoc^^'

IV

PhUosophiccU Magazine, May 1881, Sec., &o. These are only a selected few of the
papers published by the author, chosen as bearing specially on the subject of the
book.

It migbt be considered that, with the above additions, it would be
necessary to remodel the book; but these subjects absorb so much
thought and so much time (the author's health haying been affected
thereby) that this would be impossible at present. Those sections of the
book which refer ^ the general phenomena of approach to vibration have
been practically abandoned, in view of the explanation of gravitation
suggested in the subsequently published papers above named ; but this
part of the book may still be not unworthy of perusal on account of
certain truths which it undoubtedly contains. The remainder or greater
bulk of the work (with the exception of some few paragraphs, which the
author would rather were omitted, as presenting perhaps some abearance
at least of dogmatism or haste) may serve to awaken the attention and
arouse an interest in those new views towards which modem Science is
certainly tending. The author hopes that readers of his book, who may
not happen to have seen his papers (above cited) may find an interest in
perusing them, so as to form a fair appreciation of his labours as a
whole.

It might be argued, perhaps, that too much stress has been laid, in
the first part of the book, on the theory of " action at a distance," which
is now (it may be said) practically abandoned by all eminent men of
science. To this he would reply that there is a great difference between
the mere tacit or professed abandonment of a theory, and that practical
rejection of it which rouses the mind to the active search after those
conditions which can alone replace the rejected theory — the clear recog-
nition (by inevitable logical sequence) that all motions which we observe
developed in gross matter on all sides must come from the surrounding
ether or material agent in spa^, as this is the sole admissible and
conceivable conclusion by the acceptance of the principle of the
Oonservation of Energy, attended by the complete rejection of "force"

Swith its assumed spiritualistic stores of energy without motion). The
'act that Science is now notoriously advancing in this direction, should
(if anything) serve to increase rather than diminish any interest that
the author's work might have, as these considerations form the special
subject of it.

Finally, it is believed that the theory of the constitution of the ether
suggested in the present book differs from any other in at least two
essential points : viz. firstly, in the attempt to afford a proof that the
solution to the problem there suggested is (in principle at least) the sole
conceivable one, provided (let it be well understood) all ideas of " force "
in the sense of " occult action at a distance " without the aid of inter-
vening matter be unreservedly abandoned ; and secondly, the long mean
path (greater than planetary distances) between encounters assigned to
the ether particles, more especially in the subsequent papers on gravita-
tion, is, the author believes, a novel feature.

S. TOLVEE PEESTON.
December 1881.

PEEFACE.

The present work, the result of much thought and careful study,
is intended to afford an explanation or insight into the mode of
working of an important series of physical phenomena at present
referred to the theories of "action at a distance" and "potential
energy y The subject dealt with includes the general phenomena
of the aggregation of molecules, at present referred to " cohesion,*'
&c. ; and the mutual — strikingly diversified — actions of dissimilar
molecules, at present referred to "chemical affinity ,' including the
remarkable development of molecular motion taking pldce in
the phenomena of combustion and in the case of explosives,
referred to "jpotential energy;" comprising also the movements
of approach and recession of bodies in the " electric " condition
(or when " statically charged ") and the general effects comprised
under the phenomena of "attraction and repulsion"

The first part of the work contains an argument designed to prove
that the allied theories of "action at a distance" and "potential
energy " (i. e. the existence of two forms of energy, or an energy
withowl motion) are inadmissible. The second part, or greater
bulk of the work, is devoted to a consideration of the mode in
which the above-named series of physical phenomena are brought
about, or the regulating physical pBOcesses therein concerned.
It is hoped that the arguments in the first part of the work will
be received in the spirit in which they are wrritten, i. e. not in a
captious spirit, but keeping in view the attainment of truth as the
ultimate object.

PART I.

1. The influence of the theory of "action at a distance'* in
physical science is well known, and need not be commented on.
We shall proceed to examine this theory briefly. If our manner
of dealing with the subject be somewhat broad or plain-spoken,
this is with the view to clearness, our aim being simply to arrive
at truth.

Firstly, this theory assumes that one mass of matter can move
or act upon a second mass of matter, placed at a distance, without
the intervention of material or physical agency ; or the theory
assumes that a mass of matter might be surrounded to a consider*
able distance by absolutely empty space, and yet that the mass
might be put in motion without the penetration of matter in any
form into this empty space surrounding the mass.

We will take the case termed " gravity." Here it is assumed
that a mass of matter can be accelerated or put in motion at
different rates by a simple change in its position in empty space,
by which its distance from a second mass is varied, without the
necessity for the presence of a medium or anything whose physical
condition might be affected by the variation of distance between
the masses, i. e. without the necessity for the presence of matter or
any material means to produce and regulate the different degrees
of energy with which the mass is acted upon in different positions ;
or it is assumed that the mass can be acted upon or moved with
different degrees of energy (found to have a somewhat complicated
relation to the relative distance of the masses), without the
presence of any material means to regulate the varying energy
with which the mass is acted upon in the different position : in
short, a mass of matter may be wandering about in space some
thousands of miles away from anything to control its motions, and
yet it is assumed that the mass, by simply passing from one point
of empty space to another, can have its velocity adjusted in pro-
portion to the square of its distance from another mass. We can
imagine nothing more opposed to reason than this, if the question
be fairly looked at.

It is important to distinguish between the fact of this exact
adjustment taking place, and the cause, for no one doubts the
fact; but the theory would assume that there a^^ \i^ ^w::i\s^'^

physical conditions about the mass required to produce the varying
effects ; or, in other words, that by a mere change of distance the
physical effects can vary, without the physical conditions about
the mass having undergone any change. Surely the only con-
ceivable way in which the mass could be differently affected at
different distances, would be by the presence of something about
the mass, whose physical condition might be affected by the
distance, for the mass itself cannot possibly be physically affected
by the distance.

2. It is sometimes said that this is a " property " of matter or
a " law," as if to imply that this in itself constituted a reasonable
basis for the assumption or theory, but it is clear that this is merely
to assume that it is a fact; for of course a mass of matter may
be readily assumed to have the property of doing anything, how-
ever incredible ; but this would be only assuming the thing to be
a fact without a reasonable ground to support the assumption.

Surely, if a thing be stated to be practicable, the least to be
required is that some idea should be formed of the means by which
the result or mechanical end is to be attained, and this perception
of the means constitutes the sole ground to support the assumption
as to practicability. If, on the other hand, a thing be assumed to
be practicaVe without any perception of the means, then the
assumption falls away of itself from want of ground to support it.

It may be said to be a law or property of light to vary as the
square of the distance, but this does not render less essential the
existence of regulating physical conditions to produce this special
mechanical effect.

Again, in the case of the movement of approach of two masses
towards each other, it is sometimes said that the one mass
" attracts " the other, or that it is dtf£ to " attraction," as if to
imply that this constituted in some way an explanation of the
effect. To constitute an "explanation," however, something at
least must be added to our present knowledge. Before this phrase
" attraction " was applied, the remarkable effect was observed
that two masses of matter exhibited a tendency to move towards
each other, and when free to move, moved towards each other,
without anything being known as to the cause of this effect : after
the application of this phrase " attraction " the same effect was
observed with no further addition to knowledge, so that the appli-
cation of the mere phrase evidently can teach nothing. It is of
course necessary to have some phrase as a convenient means of
reference to the case, and the term " attraction " may serve as
well as any other; just as the term "repulsion" serves to refer
to the opposite movement; as, for example, the repulsion of a pith
ball by an electrified body ; but to assume that this term gave any
insight into the cause of the movement would be very like assuming
that the repulsion of the ball was due to repulsion,

A vibrating tuning-fork is known to attract a piece of card, or to

cause a piece of card to exhibit a tendency to move towards it ; but
the term " attract " can evidently give no insight into the physical
cause. The same considerations apply as regards the remarkable
tendency exhibited by a piece of iron to move towards another
piece when in that special physical state termed the magnetic
state. The phrase may be varied at will, and can avail nothing, so
long as no clear idea is formed of the means by which the
mechanical end is attained. Before the atmospberic pressure was
recognized, a pump was considered to have some mysterious power
of drawing fluids, and the effect was sometimes said to be dv^ to
"suction." It is an observed fact that the molecules of a solid
hold together in a state of cohesion ; or, although these molecules
are wholly unconnected and a certain distance apart, they are
nevertheless maintained in positions of stable equilibrium, so that a
certain resistance is encountered when the attempt is made to move
them to a greater distance apart. This resistance of the molecules
to separation is sometimes said to be dtte to "cohesion," which
certainly would have the appearance of implying that the cohesion
of the molecules was due to cohesion. It is unquestionable that a
certain abuse of terms or phrases exists, which appear in some
cases to take the place of physical causes. The term " chemical
affinity" affords another example, of which others might be given.
3. There is another point in connection with the theory of
"action at a distance." It is assumed that time is not required
for the effect at a distance to be produced. Thus, if we take the
case of an electromagnet and a piece of iron at a distance : then
when the electromagnet is suddenly put in the "magnetic" con-
dition by the electric current, it is assumed, in accordance with this
theory, that the agency by which the distant piece of iron is put in
motion requires no time to pass from the magnet to the iron. Now
surely for the piece of iron to be affected, the agency, whatever it
be, producing the effect, must cross the intervening interval to get
at the iron ; and how can it be assumed that no time is required
for the transit? It is difficult to see how this would avoid the
absurd postulate of an infinite velocity, the speciality of which
would be that that which passes would require to have the peculiar
property of occupying the beginning, the end, and every inter-
mediate point of its path at the same instant. What is it that
the theory really means to put forward ? Is it an admission of
spiritualism ? If it be assumed that intervening matter is here
not concerned in producing the movement of the piece of iron,
then how is the implied inference as to the intervention of
spiritualistic agency to be avoided ? There can be no question
that this theory is distinguished for a remarkable vagueness, and a
complete absence o£ demand for the exercise of the intellectual
powers. Can it be said, and if so in what respect, a clearer idea
admits of being formed of the means by which motion is produced^
when it is referred to "action at a distance" woA^V^t>l'SX»\^x«^^t^^^

to ** psychic force." One noteworthy point in connection with
theories of a vague nature is, that their very vagueness, in which
their real weakness consists, is employed as a defence against argu-
ment : hence the long life of such theories.

4. Another important consideration in connection with the
theory of "action at a distance," is the practically unlimited
application of which such a principle admits. It is a point very
generally recognized that all physical phenomena or eflFects are
eflFects of motion, or that physical phenomena, whatever their
diversity, are all correlated in this fundamental respect. If, there-
fore, the principle be once conceded that motion can take place
without physical agency, or that the mere presence of a mass of
matter suflSces to produce motion, then how is it possible to know
what might not occur, since all physical effects are efifeiets of motion,
or how could there be a rational guide or regulating principle to
physical causation left?

In fact, the very movements to which this theory of ** action at
a distance " is chiefly applied, viz. the movements of approach and
recession of masses and molecules of matter, constitute the funda-
mental and most important movements concerned in the working
of physical phenomena. If, moreover, these movements may vary
in energy at different points of space, or at different distances,
without regulating physical conditions, as this theory supposes,
then what result might not be attained by the free application of
this theory, which from its very nature may be made to include
all physical phenomena ?

One of the most palpable facts to any impartial observer will
be the extraordinary number of hypotheses that do exist regarding
the working of physical phenomena, all built upon this principle
or theory ; in fact, the principle from its very nature admits of an
endless variety of applications, and from the vast number of
hypotheses which present themselves by a recognition of this
theory, a certain and final solution to a physical problem is
rendered impossible. In fact, the very fertility of resource given
the fancy by this principle renders the problem insoluble. In
short, it must be plain that a principle which would put physical
causation under the control of phantom agencies, and which allows
physical effects to be brought about much according to the fancy,
itself completely precludes the possibility of determining what the
facts are.

5. There is another point in connection with this theory. If
all physical phenomena or effects be effects of motion, and if, in
any case when motion is observed to take place, a rational cause
or process capable of being appreciated by the mind is required ;
then, as a point of principle, why should not such a cause be
required in all cases, since all cases are fundamentally of the
same kind ; or how can it be logically consistent to draw dis-
tinctions when the principle involved is the same ?

Thus, if it be considered as a point of principle inconsistent or
even absurd to assume that the heat (motion) produced in a focus
of invisible heat rays has been developed without material or
physical agency ; then as a point of principle must it not be
equally absurd to assume that the motion produced in a distant
pith ball by an electrified body has been developed without
physical agency ?

6. Again, if all physical eflFects be eflfects of motion, then, in
principle, the one fundamental cause for investigation must be
the cause of motion, or the cause determining the vast variety of
motions constituting physical phenomena. To admit, therefore, a
theory which would do away with the necessity for investigating
the cause of motion, would be to admit a principle which, if carried
out universally, would close the field for physical research alto-
gether, or which would assume that physical eficcts were inex-
plicable; for if every motion were referred to this theory of
** action at a distance,' there would be no realizable physical cause
left to investigate ; and the course taken would be simply to
observe physical effects, and to apply this theory, without maKing
thereby one practical addition to knowledge as regards physicfu
causation. We merely put forward that this would be only
carrying out in its entirety a principle which has already been
carried out to a very great extent.

Thus, for example, all the varied and remarkable effects of
chemical action, or those remarkably diverse movements of mole-
cules which constitute the science of chemistry, are all referred
in one gi'eat whole to this theory of ** action at a distance."
According to this theory, it is supposed that no rational cause
capable of being appreciated by the mind exists or is necessary
to explain why one molecule should move towards another;
should move from a second, or should be indifferent towards a
third molecule. Here the effects are most complicated, and yet
take place with the utmost precision and regularity in every
instance ; in short, it would be difficult to conceive of any case
where the presence of a regulating physical agent, or a controlling
physical cause, unalterable in its nature, is more needed than
here.

The direction of the movement may even be reversed at a
certain point of space. Thus, to take the case of the component
molecules of a solid for example : then these molecules resist an
attempt to separate them, or to move them to a greater distance
apart. But when these molecules have been separated, such as
when a solid has been broken into two parts, then the molecules
resist an attempt to make them approach, or the two parts will not
readily unite again by pressure. Hence it must follow from this,
as a remarkable fact, that the direction in which the molecules
tend to move changes at a particular point of space : the moW
cules being urged towards each othei viWw. ^^d^Rfe^. ycl^^^ *^&^&

6

point, and urge:l from each other (separating) when placed
outside this point. If there be no explanation required for tliis,
then one might inquire if there be such a thing as an explanation
required for anything.

7. There is another aspect in which this theory of " action at
a distance " may be viewed, although we cannot but submit that
the above arguments constitute in themselves sufficient and
reasonable grounds for the rejection of the theory. However, as
we would not neglect any material point that might serve to
throw a true light upon the subject, we will, in conclusion, briefly
examine the theory of *•' action at a distance " in connection with
the principle of the conservation of energy ; it being evident that
two principles so intimately connected with the working of physical
phenomena must have a direct and important bearing upon each
other.

It is an admitted feict that energy is indestructible. For the
purpose of practical illustration we will suppose a special case.
vVe may imagine the charged metallic conductor of an electric
machine and a pith ball, the arrangement being supposed such
that the movement of the ball towards or from the conductor can
take place with perfect freedom, or entirely without hindrance,
the ball being supposed, by any convenient means, prevented from
coming into actual contact with the charged conductor. Then, as
is well known, when the conductor is charged, or put in the
" electric " condition, the pith ball would be impelled towards the
charged conductor, or ** attracted." If allowed to come into contact
with the charged conductor the ball would be impelled from the
charged conductor, or " repelled." It is quite indifferent whether
we consider the movement from or the movement towards. We
will accordingly take the movement towards, and suppose that the
ball is prevented from coming into actual contact with the charged
conductor, and therefore tends continually to move towards the
conductor.

If, then, we suppose that while the ball is in the nearest
proximity to the charged conductor a sharp blow or impulse be
communicated to the ball, so as to impart to it a certain initial
velocity which would carry it away from the charged conductor,
then the ball would rapidly lose the motion imparted by the
impulse ; the ball would at length come to rest, and would then
recoil or return, with freshly acquired motion, towards the
charged conductor,

8. Now the question at once suggesting itself would be, how
was this motion imparted by the first impulse lost by the ball, or
what has become of this motion ? If the theory of " action at a
distance " cannot account satisfactorily for the disappearance of
this motion, then, on this one ground alone, this theory would have
to be abandoned, and the necessary inference would at once follow,
that ifiince in accordance with the principle of conservation this

motion lost by the ball cannot have been annihilated^ or cannot
have gone out of existence spontaneously, that, therefore, this
motion must have been transferred to matter; and secondly,
therefore, that matter must exist in the vicinity of tiie ball and
electrified conductor.

These two deductions would be absolutely necessary ; for, in
the first place, in order for the motion given up by the ball to
exist, this motion must have been transferred to matter ; and
secondly, for the motion given up by the ball to be transferred to
matter, matter must exist in the vicinity of the ball.

It is unnecessary to add that it is a known fact, that the ether
exists in the vicinity of the ball, occupies the intervening space
between the ball and charged conductor, and therefore forms a
connecting link between the two, the ether even pervading the
molecular interstices of both. Moreover, it is a very generally
recognized point, that " electricity " must be some form of motion,
which motion could not possibly take place without disturbing
the ether. However, independently of these considerations, and
of the known fact of the existence of the ether, the deduction that
matter did exist in the vicinity of the ball, to which the motion
could be transferred, would be none the less a necessary one, fol-
lowing directly from the principle of the conservation of energy.

It is important, therefore, to note the intimate bearing
which the principle of the conservation of energy has upon the
theory of '* action at a distance," it being observed that the prin-
ciple of conservation requires absolutely that matter to which tl>e
motion can be transferred must be concerned in bringing the ball
to rest; while, on the other hand, the theory of "action at a
distance " assumes that matter is not concerned in bringing the
ball to rest, so that the principle of the conservation of energy
being admitted, the theory of " action at a distance " would have
to be abandoned.

9. In preference to taking this plain and straightforward course,
however, and then proceeding to investigate the special physical
conditions concerned in bringing the ball to rest, the vague theory
has been advanced that the energy given up by the ball has
assumed a different form which is not motion, or the motion lost
by the ball has been converted into something else, or the motion
is said to have been converted into " potential energy," so termed ;
and further, it is assumed that, although the motion has been trans-
ferred to nothing, yet by some unexplained process, on account of
the motion lost, the ball has acquired the power of returning
by itself to the electrified conductor at any future time, without
the intervention of physical agency.

10. Before considering this further, we may just give an
illustrative example, serving to show that in a case where the
controlling physical conditions are supposed unknown, precisely
the same appearances would present them^^Vs^^^ss»\xsL'vSia^»afc^

the electrified conductor and pith ball. We may imagine the case
of a mass of matter suspended freely, and which tends to approach
another mass, under the action of invisible matter in motion, in
any form (such as, for example, a concealed jet of air) which
impinges continually in the rear of the mass. Then one mass of
matter, tending to approach anotlier without a visible cause, the
appearance here presented would, therefore, be precisely that of a
case where the theory of " action at a distance " is applied, and by
applying this theory here (the pliysical conditions being supposed
unknown) the assumption would be, that the tendency exhibited
by the mass to approach was due to ^* attraction." If, in an
analogous manner, an impulse be supposed given to the mass in a
direction opposite to that in which it tends to move, then the mass
rapidly loses the motion imparted by the impulse, comes to rest,
and finally recoils or returns, with freshly acquired motion, by the
same path. The motion lost by the mass of matter during its
recession was transferred to the rebounding molecules of the
invisible air-jet ; the motion acquired by the mass during its
return having been (conversely) transferred from the molecules of
the air-jet to the mass.

Here, therefore, it may be observed that precisely the same
eifects present themselves as in the previous illustrative case of
tie electrified conductor and pith ball, which exemplifies the
general case where the theories of " action at a distance " and
"potential energy" are applied. If, therefore, we apply this
theory to the case of the mass and air-jet (the physical conditions
being supposed unknown), then the assumption would be that the
motion lost by the mass during its recession, although not annihi-
lated, and ceasing to exist in the mass itself, was nevertheless not
necessarily transferred to anything else ; but that this motion
took up a different form (" potential energy," so termed), and that
thereby the mass of matter acquired the power of recoiling or
returning through the same path, without the intervention of
physical agency, the something which is not motion being assumed
to be con verted, back into motion at the recoil of the mass.

11. If, now, the above theory appear wholly vague and quite
inadequate to replace the controUmg physical conditions, after
these controlling physical conditions have been recognized (as in
the above case), then, as a point of principle, the theory can be
none the less open to objection in the case of a similar effect,
where the existence of controlling physical conditions is not
apparent; or, in other words, if the necessity of controlling
physical conditions to produce a given physical effect appear
obvious, after their existence has been recognized, then the
necessity for the existence of these controlbng physical conditions
cannot be less imperative in the case of a similar effect, where
their existence is not recognized ; and surely it must be an
important point to recognize the necessity for the existence of a

9

thing hefore it makes itself apparent^ for this is the sole means
whereby the attention can be directed towards its discovery.

12. In fact, this theory of the existence of "potential energy,"
or an enei^ without motion, in regard to vagueness, cannot be
said to diner from the theory of "action at a distance," which
it is intended to support, the same system of procedure being
adopted, viz. that of assuming a thing to be practicable, where
the sole ground upon which the assumption as to practicability
can rest — a conception of the means — is wanting. How can it
le possible to guard against error, when such a system of pro-
cedure is adopted, if, indeed, it be not very like drifting into
error? Nothing can be easier than to put forward assump-
tions of this character, and at the same time nothing is more
certain than that there is no teaching of nature, however plain ;
no truth but what is subject to be disguised by such a system
of procedure. The theory, indeed, conveys no definite idea of
the nature of the form which the motion is assumed to have
taken up.

The very assumption of the existence of energy in a double
form, or the attempt to attach two ideas to the fundamental
conception energy, or to assume that two kinds of energy exist,
cannot but be regarded by itself as sufficiently questionable.

If in the illustrative case of the electrified conductor and
pith ball we disregard, as in accordance with the theory, all
influence of the presence of the ether or of anything to which
to transfer the motion of the ball ; then when the ball comes
for an instant to rest previous to its recoil, we have only matter
at rest and empty space, yet the theory puts forward that the
assumed form which the motion has taken up exists here ; and
further, that this form resolves itself back into motion at the
recoil or return of the ball, it being assumed in accordance with
this theory that the presence of matter or of a physical agent is
not required to transfer the motion to the ball at its recoil.

It would be surely difficult to imagine anything more vague
than this, or any assumption or theory where the absence of a
reasonable ground or basis to support it is more apparent than in
this case ; in fact, the theory may De well compared in this respect
with the connected theory of " action at a distance," it being also
well to observe, as a noteworthy and significant fact, the intimate
dependence which exists between these two theories, the abandon-
ment of either involving the abandonment of both.

It is moreover impossible to doubt that the question as to
\\ hether these two theories are admissible or not, admits of being
finally decided as a point of reasoning, for there can exist but one
correct method of viewing any subject or question whatever.

10

PART II.

SECTION I.

13. We may now enumerate the main physical conditions
that would require to be satisfied in order to replace the above
theories by physical causes capable of a rational appreciation, and
of affording an insight into the mode of working of physical
phenomena.

As a fi^rst condition, we require the existence of a physical agent
capable of transmitting motions to a distance with speed and
facility, in order to refer to physical agency all the eflTects at
present brought under the theory of " action at a distance." As a
second condition, this physical agent must be shown to be capable
of enclosing a store of motion of a very intense character,
competent to produce all those. forcible molecular and other move-
ments of matter exhibited in such eflTects as the phenomena of
chemical action, the ** electric " motions, combustion, the remark-
able development of molecular motion observed in the case of
explosive compounds, such as in the explosion of gunpowder, and
other numerous and striking phases of motion witnessed on all
sides. Thirdly, this physical agent will have to be proved to be
competent to exert an intense pressure upon the molecules of
matter, as consonant with the very forcible character of the static
effects exhibited in "cohesion," and the stable aggregation of
molecules generally : and finally, these several physical qualities
of the agent will have to be shown to be capable of existing
harmoniously together and consistent with an extremely low
density in the agent.

14. Physiccu Constitution of the Ether. — The ether being the
means by which the entire energy received from the sun in the
form of heat and light, &c., is transmitted to the earth, the ether
therefore may be properly regarded as the most important of
physical agents; tnis agent being a most influential one and
everywhere present, to the ether therefore we must look as the
agent concerned in the various molecular and other movements of
matter, including the physical effects produced at a distance
generally.

11

15, Now in dealing with the problem as to the
constitution of the ether, or the physical basis upon wl
qualities depend, it may be shown as a noteworthy point that if
we exclude the theory of " action at a distance," and consequently
the theory of " potential energy," then this physical problem will
admit of only one solution, or the problem admits of being solved
but in one special way. This point is one of importance and
interest, since if it be recognized that reasonable grounds exist for
rejecting the above theories, then the deduction would follow with
certainty that this solution to the problem is the true one or the
actual fact, this following necessarily from the circumstance of the
existence of but one solution.

To those who are not prepared to reject the theory of " action
at a distance " on purely abstract grounds, the simple course lies
open of putting the results necessarily attendant on this solutfon
to the problem to the test of observed facts. Even if merely for
the sake of argument we put for an instant the question as to the
admissibility of the theory of " action at a distance " out of sight
altogether, it cannot but be regarded as a point of interest that
by the rejection of this theory but one solution to the problem
should exist, and therefore that if this theory be unfounded, this
solution to the problem must be the true one.

16. On the other hand, it may be shown that if the theory of
" action at a distance " be admitted, then a final solution to the
problem is no longer possible, from the fact that no definite limit
exists to the number of assumptions or possible solutions, and
therefore it becomes impossible to fix finally upon any one, since
the same end might be attained in a great variety of ways. This
will become apparent after the question has been examined.

Thus in the first place it would be impossible to decide the
fundamental question whether the normal state of the component

E articles of the ether is a state of motion or a state of rest ; for
y the hypothesis of non-material agencies, the particles might be
at rest and yet be capable of expanding the agent and producing
physical eflTects of pressure, &c. If it were assumed as a mere
hypothesis that the particles of the agent were in motion in their
normal state, then it would be impossible, by the admission of the
theory of ** action at a distance," to fix finally upon the character
of this motion ; for it is evident that the particles might bfe either
moving in straight lines, or in curved paths whose character would
depend 6n. the values or intensities assumed to the non-material
agencies in difi^erent points of space, i.e. dependent on the assumed
mode of variation of the intensity of the agency by a change of
distance of the particles, which mode of variation the theory of
" action at a distance " assumes to be purely arbitrary, or it might
vary as the distance, as the square of the distance, &c.

If, again, the inquiry were directed as to the cause producing
the remarkable elasticity of the ether, a fact ^^xon^^Vj^ ^^ 's^^'^

12

with which this agent can propagate waves, such as waves of light,
then a final solution to this question would be equally impossible,
for it would be impossible to decide whether to refer the elasticity
of the agent to a motion of its component particles or not, since,
in accordance with the theory of '* action at a distance," the
particles might be at rest and yet produce any degree of elasticity ;
and if in motion there is scarcely an assignable limit to the variety
of motion. In short, the practically unlimited field for speculation
which this theory brings with it precludes the possibility of a final
decision, and the maze of hypotheses presented by it renders
theoretic reasoning of little avail.

17. If, on the other hand, we reject the theory of " action at
a distance " and the connected theory of " potential energy," then
a definite course lies open. Considering first the question whether
the normal state of the component particles of the ether is a state
of motion or a state of rest ; then it naay be shown that taking the
observed fact of the elasticity of the ether, it admits of being
deduced from the principle of the conservation of energy that the
normal state of the ether particles is a state of motion.

18. If any portion of an aeriform medium, such for example
as a portion of air be supposed confined within a receptacle which
is not rigid, then the quality of elasticity enables the mass of
confined air to expand when the outer air pressure is in any way
removed, in which act of expansion motion is communicated to
the sides of the receptacle, which yield to the internal pressure.
The quality of elasticity in an aeriform medium, therefore, enables it
under certain conditions to communicate or develop motion. Now
it follows from the principle of conservation that the previous
existence of motion is the absolutely essential condition in order
for motion to be developed, for unless motion previously existed,
motion could not be expended in the act of developing motion (as
in the act of expansion of a gas), but this is an absolutely necessary
condition, for otherwise the sum of energy could not remain
constant, but there would be a creation of motion out of nothing.
The quality of elasticity, therefore, in an aeriform medium by
which it can expand and fill a larger portion of space than it
occupies under normal conditions, and in which act motion is
developed, must be dependent on a motion previously existing.
Hence, since it is an observed fact that the ether possesses in its
normal state the quality of elasticity, the inference necessarily
follows that the normal state of the ether particles must be a
state of motion,

19. We have next to inquire as to the mode or character of this
motion. It is an admitted self-evident principle that a mass of
matter is incapable of itself to change the direction of its motion.
Absence of change in direction being the characteristic of the
straight line ; it therefore follows that a mass or particle of matter

13

moving in absolutely free space, and unobstructed by other matter
in any form, will continue to move in a straight line until by
encountering matter in some form its direction of motion may be
changed. From this the inference necessarily follows that the ether
particles move in straight lines.

20. The only remaining question is as to the general
direction of the motion. Now, it is at once clear that this motion
must take place in such a way that when any appreciable portion
of the medium made up of a large number of particles is
considered, this portion oi the medium can, as a whole, maintain
a fixed position, or can be in equilibrium of pressure with the
surrounding medium. Now, this maintenance of a fixed position
by the portion of the medium or the maintenance of an
equilibrium of pressure on all sides can evidently only be satisfied
on the condition that the particles are moving in every possible
direction, and not in any one particular direction in preference to
another, the particles continually interchanging motion or re-
bounding from each other in every direction, and thereby propa-
gating an equal pressure on all sides.

There would obviously be no reason why the particles should
be moving in one direction more than in another; and, moreover,
it may be shown that there exists a special self-acting tendency
for this motion of the particles to be maintained towards every
possible direction. This results from the consideration that the
equilibrium of pressure depends on the fact that the motion takes
place towards every direction, and a motion of any notable
number of particles towards one special direction would neces-
sarily cause a disturbance of the. equilibrium of pressure, and this,
by causing a yieldmg of the medium in the direction of the
greatest pressure, would speedily cause a readjustment of the
pressure; and since this irregularity of pressure is necessarily
self-righting, the irregularity of the motion of the particles on
which the pressure depends must also be self-righting, equilibrium
of pressure being only restored when the irregularity of motion
has corrected itself, i. e. when the motion of the particles takes
place towards all directions.

The existence of this mechanical self-adjusting tendency will
be very apparent if we consider any special case whatever. Thus,
supposing, merely for illustration, the component particles of a
single cubic foot of the medium to be all moving at a given
instant in one common direction, then by this procedure the
transverse pressure exerted by this cubic foot of the medium
would cease, for a pressure evidently cannot be exerted at right
angles to the direction of motion. The pressure of the surround-
ing medium would therefore cause this cubic foot of the medium
to collapse laterally (due to the absence of a lateral opposing
pressure), and in this act the particles of this cubic foot of the

14

medium would receive a forcible transverse acceleration, which
they previously wanted, the abnormal movement being thus soon
corrected and the equilibrium of pressure restored. It is clear
that in the actual fact no notable irregularity in the motion can
accumulate, for the rapid interchange of motion going on among
the particles necessarily corrects the slightest disturbance of the
equilibrium of pressure immediately on its occurrence, a continual
self-acting adjustment thus going on, which entirely prevents an
abnormal movement of the particles from developing itself.

21. To summarize therefore : the inferences are, first, thai the
normal state of the component particles of the ether is a state of
motion; second, that this motion of the particles takes phice in
straight lines; and third, that this motion takes place towards
every possible direction. This deduction as to the physical con-
stitution of the ether, to which we have been led without choice,
since (the theory of " action at a distance " being excluded) the
problem admits of but one solution, resembles in its nature the
theory applied by Joule and Clausius to gases. This theory would
accordingly have a general application, or would be applicable to
all aeriform media, one apparent point in the theory being its ex-
treme simplicity. We may note, that since when the medium is
in its normal state the motion of the component particles takes
place towards every possible direction, the particles would there-
fore be accelerated and retarded both in transverse and in longi-
tudinal directions at the passage of waves.

22. The fact of the continuance of the motion of the ether
particles without decrease or loss becomes very apparent when it
IS considered that one particle could only lose its motion by tians-
ferring that motion to another.

The fact that a mass of matter will remain in motion until
acted on by a physical cause appears sometimes to be regarded as
a less self-evident truth than the fact that a mass of matter will
remain at rest until acted on by a physical cause ; but it may be
shown that the two cases are equally axiomatic, for a change fro^i
any given degree of motion to rest is precisely the same change
(though inverse) as a change from rest to that same degree of
motion. Hence if it be looked upon as self-evident that a mass of
matter will not of itself change its state from rest to motion, then,
to be consistent, it must be looked upon as equally self-evident
that a mass of matter will not of itself cnange its state from motion
to rest, or the mass is wholly incompetent to change its state at all.

23. It is a known fact that the quality of elasticity is deve-
loped in the ether to a high degree : hence it would be reasonable
to expect from this that the motion upon which this elasticity
depends must be an extremely rapid motion. The inquiry there-
fore suggests itself, whether there is any observed fact that would
indicate the value of this motion, or the mean speed of the ether
particles in their normal state.

15

Now the velocity with which the ether transmits a wave or
impulse has been measured, this velocity being about 190,000
miles per second, in round numbers. The speed with which a
small impulse can be conveyed from particle to particle in the
normal state of the ether must clearly depend on the speed with
which an interchange of motion can effect itself between the
particles, i. e. must depend on the normal speed of the particles
themselves. Hence the deduction follows that the normal velo-
city of the ether particles must at least equal that with which
they can transmit a wave (such as a wave of light), for on no
other physical condition could any change of velocity in the
ether particles, however slight, produced by some disturbing cause,
be propagated to a distance from particle to particle at the
above velocity ; indeed, it is necessary to infer that the actual
normal velocity of the particles must be somewhat in excess of the
above, since the wave is not transmitted by particles which are all
moving in the direct line of propagation of the wave, but also by

E articles which are moving obliquely. The wave could evidently
e transmitted forward at a speed equal to that of the particles
themselves, only on the condition that they were all moving in
the direct line of propagation of the wave, which is not the fact.

This resembles the parallel case of an air wave (such as a
wave of sound), which is transmitted at a slower rate than the
mean velocity of the air molecules in their normal state, for this
velocity has been fixed at about 1600 feet per second, while the
velocity of propagation of a wave, such as a wave of sound, is less
than this, or about 1150 feet per second.

24. The above limiting value for the normal velocity of the
ether particles will probably appear inordinately high on the first
consideration of the subject; but it is essential that the special
circumstances of the case should be taken into account. Thus,
owing to the extreme minuteness, or very small mass, of the ether
particles as compared with gross molecules, the absolute value of
the energy possessed by each ether particle, even when moving at
the above velocity, may be extremely small, and may possibly be
even less than tne energy possessed by an air molecule when
moving at its normal velocity ; for there is no limit to the extent
to which the energy possessed by each particle may be conceived
to be reduced by a sub-division of the matter of which the ether
consists, and yet this does not detract in the least degree from the
total sum of energy. The molecules of gases are known to possess
a higher normal velocity as the molecular density diminishes.
The exceptionally low density of the ether would rather lead a
high normal speed for the particles to be expected than otherwise.

An extensive state of subdivision would also have the effect
of so curtailing the mean length of path of the particles, or of
restricting the distances which the particles can move before being
intercepted by other particles within such narrow Ivixdta^^v^^^^-

16

tually to conceal the existence of this motion from the direct
evidence of the senses.

25. The above deduction, as to the high speed of the ether
particles in their normal state, throws at once a light upon the
existence of a vast store of energy in space of a very intense
character, competent to produce the most forcible observed mole-
cular motions, such as the phenomena of chemical action, com-
bustion, the explosion of gunpowder, and other remarkable cases
of the development of motion or work, all such effects finding
their explanation in an interchange of motion between the ether
euad the molecules of matter under special conditions, which we
shall have to consider farther on. The special physical qualities
of the ether may be shown to render it an agent admirably
adapted, in a mechanical point of view, to fulfil its varied
functions, or it may be properly contemplated as a piece of
mechanism specially adapted to its work.

26. In considering the bio:h normal velocity of the ether par-
ticles, it is to be expected beforehand that this agent must exert
an extremely forcible pressure upon the molecules of matter, even
if every allowance be made for the extreme low density of the
agent ; for it is impoiiant to note that the pressure exerted is as
the square of the speed of the particles of the agent, and therefore
the pressure rises m a very rapid ratio as the speed increases ; so
that taking into account this fact, in conjunction with the high
velocity of the particles, we must be prepared to find this pressure
will have a very high value. In looking to physical phenomena
for an indication of this pressure, and also with the object, if pos-
sible, of arriving at a limiting value for its intensity, or the value
which this pressure must at least attain on the lowest computation,
we will consider one observed fact.

27. Steel of the best quality, in the form of fine wire, has been
known to bear a tensile strain represented by not less than 150
tons per square inch,* and even this cannot be said to be the limit
to the tensile strength of steel, since the tenacity obtainable
increases as the diameter of the wire is reduced.

We will consider the case when a strain is applied to such a
wiije until rupture ensues ; then it is necessary to conclude that
the molecules of the wire are, before the strain is applied, at a
certain distance from each other, for the wire can contract sensibly
by a change of temperature. If, therefore, these molecules were
surrounded by absolute empty space, tb^e would be no conceivable
physical cause why they should resist an attempt, however feeble,
merely to change their positions in space ; but it is scarcely neces-
sary to add that the molecular interstices of the wire, as is the case
with matter generally, are necessarily pervaded by the ether, which

* For a special example, see * Telegraphic Journal ' (May 1, 1874). The tenacity
of the wire in question (No. 22 B.WT.G. diam. = 0*03 inch) might have been in-
creased, bad pliaoility been no consideration.

17

exercises its pressure upon the molecules of the wire, which mole-
cules are also in a state of energetic vibration, as indicated by the
forcible ether waves emitted (radiation of heat). The ether there-
fore which pervades the wire cannot but be disturbed by the
movement attendant on the separation of the molecules of the
wire, and is the one agent to which the forcible resistance encoun-
tered in separating these molecules can be referred.

In order to view the subject in its simplest form, we will only
regard two transverse layers of molecules forming the cross section
of the wire ; or we may even imagine, merely for the purpose of
illustration, two such layers to have been separated from the wire,
and that now a strain is applied in order to separate these two
layers of vibrating molecules from each other. Then the deduction
follows as a necessary one, that when by the action of the applied
strain the distance of these two layers of vibrating molecules has
been increased, that this change of distance has brought about a
change in the distribution of the ether pressure, or has disturbed
the equilibrium of this pressure, such that when the resistance has
attained a maximum, a reduction of the ether pressure upon the
adjacent halves of the component molecules of the two layers,
amounting to 150 tons per square inch, has been effected, so that
the normal ether pressure upon the outer halves of the molecules
forming the two layers tends, with the above force, to resist the
separation of the molecules.

As to the precise physical process by which a reduction of the
pressure of the intervening medium can take place in the presence
of vibrating matter, we shall reserve the consideration of this point
for the present ; but it may be noted that the inference is none
the less essential, that a reduction of the ether pressure does
take place in the presence of the opposed vibrating molecules of
the wire, since there remains no other conceivable means of
explaining in a realizable manner why these portions of matter
(molecules), already completely disconnected from each other in
the normal state of the wire, should require this enormous force to
shift their positions in the act of breaking the wire, unless in this
act there were something further to be accomplished than merely
to change the positions of the molecules in space.

28. Now it is to be observed that the aoove illustrative case
only gives the amount of the reduction of the ether pressure, or
the difference of pressure upon the opposite halves of the mole-
cules, and not the total or normal ether pressure, which is the
point we are investigating, and it might well be that this differ-
ence of pressure only amounted to a small part of the total ether
pressure.

That this difference of pressure is far from representing the
total ether pressure is shown by a consideration of the case of
chemically combined molecules, the force required to separate
molecules " chemically combined," as it ia 'totTCkfe^, \^\:ci^^ ^>5a» ^

18

known fact, very much greater than in the case of ** cohesion," so
termed ; indeed it is impossible by ordinary mechanical means to
separate chemically combined molecules, whereas this result is
attainable with comparative facility in the case of ** cohesion."
The very much greater intensity of the force that would be
required to separate chemically combined molecules is well shown
when the converse process takes place. Thus the explosive energy
and intense heat developed at the approach of oxygen and hydro-
gen molecules, when the mixed gases are detonated, clearly shows
the high intensity of the force that would be required to separate
these molecules from each other, thereby showing the high intensity
of the controlling ether pressure, and indicating that the difference
of pressure to be overcome in separating the molecules in this case
must be many times greater than in the case of "cohesion," as in
the example given of steel. If we suppose the intensity of the
pressure to be overcome in the case of the separation of the mole-
cules of oxygen and hydrogen, one of the most powerful cases of
chemical union, to be only three times greater than that overcome
by the separation of the molecules in the example given of the
steel wire, then this would give 45D tons per square inch as the
difference of pressure effective in the case of the molecules of
oxygen and hydrogen.

This is, however, not the total or normal ether pressure, but
only the effective difference of pressure ; however, as our object
is only to arrive at a limiting estimate for this pressure, or to fix
upon the lowest value consistent with what observed physical facts
would require, wo will accordingly take in round numbers the
estimate of 500 tons per square inch as a limiting value for the
ether pressure, having thus valid grounds for concluding that this
estimate is within the facts as they actually exist.

We might have noted in the example given of the steel wire
that there are lateral interstices between the molecules, so that
the entire estimated cross section of the wire is not available, and
therefore for this cause the difference of ether pressure effective in
this case must have been to a certain ext.ent underrated.

29. We are prepared for the above estimate as to the value of
the ether pressure being received with a certain amount of incre-
dulity, at all events at the outset ; indeed, the existence of such an
intensity of pressure as this may well be suflBcient at the first
thought to strike one with astonishment ; but it is to be noted
that, however great this pressure might be, it could not make
itself palpable to the senses, for since the ether penetrates the
molecular interstices of matter, its pressure is equalized on all
sides. The air cannot penetrate with freedom the molecular
interstices as is the case with the ether, yet a pressure of the air
amounting to several tons on the human body can exist without
the perception of the senses ; how much more cause, therefore, is
there tor the perfect concealment of the existence of the ether

19

pressure, which is exercised against the molecules of matter them-
selves, a perfect equilibrium existing? It is therefore certain
beforehand that the mere evidence of the senses cannot affect this
question at all.

From purely a priori considerations the existence of a high
pressure cannot be said to be less likely than a low pressure, or
Weed any one particular value for the ether pressure be said to
be more probable than another. In the object, therefore, to
arrive at an estimate or limiting value for this pressure, we must
consider solely observed physical facts, and be guided thereby.

It will be found that after the problem has been considered in
its other aspects and the special functions of the ether in phy-
sical phenomena have been taken into account and weighed, the
more apparent will become the mechanical fitness of this high
pressure, whereby this great physical agent is adapted to act
forcibly upon the molecules of matter ; whether it be to control
these molecules forcibly in stable equilibrium, as illustrated by
the stable aggregation of molecules in " cohesion," ** chemical
union," &c. (i. e. the general phenomena of the aggregation of
molecules) ; or to produce forcible dynamic effects when the
equilibrium of pressuire is disturbed, as illustrated by the forcible
movements of the molecules of matter exhibited in the varied
phenomena of chemical action, combustion, the effects of ex-
plosives, &c.

30. Density of the Ether. — It is a known fact that the density
of the ether is very low, this agent being thus suited to afford free
passage to cosmical bodies travelling at high speeds, the planets,
&c. In order, therefore, to be consistent with observed facts, it
will be essential to show that the existence of the high static
pressure as above deduced is compatible with the low density of
the ether.

Though pressure is due to motion, we use the term " static "
pressure for convenience, and in the same sense as it might be
applied to the pressure of a confined gas, due to the motion of its
molecules.

31. The mean density of the air at the earth's surface is known,
and the normal velocity of the air molecules giving a pressure
of 15 lb. per square inch has been deduced as 1600 feet per
second, in round numbers. The pressure of the ether as of any
aeriform medium being proportional to the square of the velocity
of the component particles, and in the ratio of the density: taking,
therefore, as previously, the measured speed of a wave of light as
the lowest limit for the speed of the ether particles, we will, in the
first place, consider what the density of the ether would be if it only
gave a pressure equal to that of the atmosphere. It is evident,
therefore, that in order for the ether to produce a pressure equal
to that of the atmosphere, the ether density would require to be
so much less than the atmospheric deiisvt^, ^^ \Xv^ ^a^^evx^ s^\*^^

20

normal velocity of the ether particles is greater than the square of
the normal velocity of the air molecules. Taking, thererore, the
square of the velocity of the ether particles (in feet per second),
and dividing it by the square of the velocity of the air molecules

(in feet per second) we have (1^0000 X^5280 )J^^ 393,120,000,000,

or this result expresses the number of times the ether density
would require to be less than the atmospheric density, in order for
the ether to give a pressure equal to that of the atmosphere (15
lb. per square inch). This density expresses such an infinitesimal
amount or almost vanishing quantity, viz. a density upwards of
three hundred and ninety thousand millions of times less than that
of the atmosphere, that the result can scarcely but be regarded as
a fiction ; indeed, a bare consideration of the result by itself would
almost warrant the inference that the ether pressure must be a
considerable multiple of the atmospheric pressure, if only to bring
up the ether density to a reasonable amount.

32. We will, accordingly, now take the value for the ether
pressure (500 tons per square inch) previously fixed upon as the
lowest limiting value, and we may then deduce what the density
would amount to, in order to give this pressure. Pressure being
directly proportional to density, the above value for the ether
density corresponding to a pressure of 15 lb. per square inch
would therefore, to give a pressure of 500 tons per square inch,
have to be increased in the ratio of these pressures : or we have
1 ^ 500 X 2240 1 .

393,120,000,000 \ 15 5;26i:800' ^"^ ^^"^ ^^"^^ '^'^^'

cates that the density of the ether giving a pressure of 500 tons
per square inch, would only amount to s^^X^ao P^^t of the
density of the atmosphere. This value for the ether density,
being upwards of five million two hundred thousand times less than
the atmospheric density, represents a density so insignificant as to
be less than that of the best gaseous vacua, for this ether density
corresponds to a rarefaction of the air carried to xyg^yoo of an
inch of mercury. If we take a fairly good air-pump vacuum at
Y^ of an inch of mercury, then 'this ether density represents a
rarefaction carried 1720 times farther.

Hence we may observe, therefore, the perfect mechanical possi-
bility of the existence of a very forcible ether pressure, consistent
with the known fact that the density of the ether is extremely
low ; a pressure of an intensity adequate to account for the stable
and forcible character of the eflfects exhibited in the phenomena
of " cohesion," and the general phenomena of the aggregation of
molecules, which may be classed under the ** static " eflfects of the
ether; as the other physical eflfects, such as the general pheno-
mena of chemical action, combustion, &c., may be classed under
the ** dynamic" eflfects of the ether. The fact that pressure
increases in the rapid ratio of the square of the speed of the

21

particles of the agent is a most important one, as this renders

Eossible the attainment of a very forcible pressure with the aid of
ut a small quantity of matter whose normal velocity is a high one.

33. In connection with this subject, it may be of interest to
contemplate the possibility of the following as a physical problem.
If we suppose a given mass of matter and a given volume of
space, the volume of the space being supposed vastly greater than
that of the mass of matter. Then it becomes possible, by the sub-
division of this mass of matter (which may be readily conceived to
be carried out to any extent), to pervade the entire volume of the
space with matter, or there is no limit to the degree of close
proximity into which the particles of matter pervading this volume
of space may be brought by continued subdivision, the approach
of the particles going on continuously without limit as the sub-
division progresses. Thus, with a given mass of matter there is
no limit to the extent of space that may be pervaded by matter
by continued subdivision, or there may be no appreciable portion
of the vast volume of space but what contains myriads of particles
of matter. The normal state of this finely subdivided matter may
be conceived to be a s'tate of motion or a state of rest ; if a state
of motion, then we may observe the physical possibility of the
existence of a store of energy of an extreme intensity, and which,
from the minuteness and small length of path of the moving
particles, must be concealed ; this motion being also necessarily
attended by the production of an intense and at the same time
evenly balanced pressure, the smoothness and uniformity of the
pressure, and the consequent concealment of its existence from
the senses, being more and more complete as the subdivision
progresses.

34. Many considerations point to the conclusion that the state
of subdivision in the case of the ether is extreme, or that the ether
particles are incomparably more minute than the molecules of
matter. In the first place, the ether could not well otherwise
penetrate with facility the molecular interstices. Secondly, the
known fact that the density of the ether is very low, points to the
conclusion that the ether particles are very minute, for if this
were not the case, the mean distance of the particles would
necessarily be inordinately great. Now, the observed extreme
steadiness of the effects due to the ether pressure, as exhibited in
the phenomena of " cohesion," &c., makes the inference necessary
that the mean distance of the ether particles cannot be great, but
that the mean distance of the particles is probably contained
many times within the limits of space which a molecule of matter
would occupy, and that, therefore, so much the more must the
particles themselves be small compared with molecules.

It is clear that if the mean distance of the ether particles bore
any near proportion to the dimensions of molecules, then the
number of particles impinging against the molecxvV^ ^^^vsJl^ \sRR«a»-

22

sarily fluctuate or vary considerably at each instant, which would
be quite incompatible with the maintenance of a steady pressure
against the molecule. The mechanical condition required for the
maintenance of a steady and constant pressure against a surface
must evidently be that the number of particles impinging against
the surface is on an average the same at each instant, and this
condition can only be fulfilled when the mean distance of the
impinging particles is small relatively to the extent of the surface,
and the number of the particles is therefore great; just as, for
example, the force with which two hemispherical cups, when
evacuated, are pressed together by the impacts of the air mole-
cules upon their outer surfaces, could not possibly be steady and
constant, if the mean distance of the air molecules were not incom-
parably less than the dimensions of the surfaces against which they
impinge. The same considerations precisely in principle apply
in the case of the action of the pressure of the ether upon mole-
cules, or the mean distance of the ether particles must, to render
possible the maintenance of a steady pressure, be much less than
the dimensions of molecules. If, therefore, the mean distance
of the ether particles be small compared with the dimensions of
molecules, how much more must the particles themselves be small
compared with molecules, and this more especially since the known
low density of the ether renders the inference necessary that the
dimensions of the ether particles must be small compared with
their mean distance? Analogy would also be in favour of the
above conclusions, for just as the mean distance of the air mole-
cules is extremely small compared with the length of a wave of
sound, so the mean distance of the ether particles is extremely
small compared with the length of a wave of light. This extreme
minuteness of dimensions is at the same time the fitting mechanical
condition adapted to a high speed for the particles, as by this
extremely subdivided state of the matter forming the ether, the
energy almost vanishes as regards each ether particle taken
separately, and yet subsists as a whole to its full value ; or by this
minuteness of the particles or extensive state of subdivision, the
motion goes on, as it were, so smoothly and equably as to be
imperceptible, and the equilibrium of masses and molecules of
matter (excepting under special conditions) is not disturbed
thereby.

35. Let us suppose, for the purpose of illustration, that it has
been possible to form an air vacuum corresponding to 172^000
of an inch of mercury. Then the amount of air thus left in the
receiver, or the sum of the masses of the residual air molecules,
would equal the sum of the masses of the ether particles, or the
quantity of matter represented by the ether contained within the
same receiver, this being in accordance with the limiting value
for the ether density already fixed upon. Now the matter repre-
sented hy these air molecules contained within the receiver wnen

23

compared with the equal quantity of matter in the form of ether
contained within the same space, represents, on the one hand, a few
extremely large masses of matter possessing an extremely slow
speed; on the other hand, a large number of extremely small
masses of matter possessing a very high speed.

If now we imagine, merely for illustration, each of these air
molecules to be subdivided into a million parts, and that the
speed of each component part has been increased a thousand times.
The presence of the ether within the receiver may be left out of
account for the present. Then by this imaginary process of sub-
division, the mean distance of these parts of matter (which we
shall terra "particles") would be so reduced as to bring these
particles into closer proximity than the molecules of air outside
the receiver (the mean distance of the particles of the subdivided
matter being inversely as the cube root of their number). The
pressure against the interior of the receiver, which is as the square
of the speed of the particles, would now be increased a million-
fold ; and yet this result is attahied without any increase in the
absolute value of the energy of each particle, for the energy has,
by the reduction of mass, remained precisely the same for each
particle as before, although the total energy has become vastly
greater, this energy being now subdivided among a large number
of particles, and the pressure maintained by a greatly increased
number of moving particles.

We might imagine this process of subdivision, or this reduction
of mass combined with increase of speed, to go on progressively,
and thus the total energy would be continually increasing, and the
mean distance and mean length of path of these small moving masses
or particles would be continually diminishing, and therefore the
concealment of this motion from the senses would be more and
more complete. The pressure would continually rise in intensity,
and at the same time become more even and perfectly balanced as
the number of particles increased.

We might thus imagine this process to go on progressively,
until at length the dimensions, mean distance, and speed of tne
ether particles themselves had been reached; or it is possible
thus step by step to arrive at a just conception of the wonderful
intensity of the'store of energy that is rendered physically practi-
cable, and the high static value of the pressure that may be
reached, under the simple mechanical conditions of an extensive
subdivision of matter combined with a high speed.

24

SECTION 11.

36. Propagation of Waves. — We have now to consider briefly,
in general principle, the mode or physical process by which varia-
tions of velocity produced in the particles of an aeriform medium,
including those periodic increments and decrements of velocity
termed "waves," are propagated to a distance by the medium.

We may, as an illustrative example, take the case of a tuning-
fork vibrating in air. Then it is to be noted that before the prong
is put in motion the air molecules are already in motion (having
a speed of about 1600 feet per second), rebounding from the prong
in all directions and exerting an equal pressure.

Then, after the fork has been put in vibration, if we regard
one forward movement or semiVibration of the prong, then the
rebounding air molecules being struck by the prong, receive an
increment of velocity (small compared with their normal velocity).
This increment of velocity is instantly transferred to the neigh-
bouring air molecules in the collisions (mutual exchange of
motion) continually occurring ; this transference of motion from
molecule to molecule taking place in accordance with the simple
principles of impact in the case of equal masses. The air molecules
next the prong, therefore, lose their increment of velocity by trans-
ferring it to the molecules in advance, the molecules returning
to the pronff with their normal velocities to receive a fresh
increment, which they again transfer, &c. ; and thus during
the advance of the prong a succession of small increments of
velocity is imparted to the air molecules in the form of a pulse
or wave, whicn is transmitted through the air by exchange of
motion with a velocity dependent on the normal velocity of the
air molecules. Since the air molecules forming this pulse or
half of the wave possess, during the interval occupied by the
passage of the pulse, a velocity slightly in excess of that of the
molecules around them, this portion of the wave is somewhat
pushed forward, and a "condensation" is the result of the
increment of velocity.

We have up to this point regarded one forward movement or
semivibration of the prong: the latter gi-adually comes to rest
before commencing its backward movement, ana thus the first
part of the wave is succeeded by a portion of air whose molecules
have received no perceptible increment of velocity. On the prong
commencing its backward movement to finish one complete vibra-
tion, the impinging air molecules now striking against its receding
surface lose a portion of their normal velocity by transference to
the prong, the decrement of velocity thus sustained by the air
molecules being transmitted in precisely the same manner by

25

exchange of motion from molecule to molecule through the
surrounding air ; and since the air molecules forming this portion of
the wave possess during the passage of the wave a velocity slightly
less than that of the molecules in the advanced part of the wave,
the mass of air is accordingly shifted backwards m relation to the
advanced part of the wave, a " rarefaction '' being the result.

37. The principle involved admits of further illustration from
a somewhat different point of view. Since the condition for the
equilibrium of pressure of an aeriform medium requires that the
particles should not be moving in one special direction in prefer-
ence to another, but in every possible direction, it follows, there-
fore, that if any imaginary straight line be taken in an aeriform
medium, such as the ether for example, then since the particles
are moving in every possible direction, and the medium is in
equilibrium of pressure along this line (as in every direction),
there must therefore be at any given instant, when a large
number of particles are taken, on an average as many particles
whose direction of motion is towards one extremity of the line, as
there are particles whose direction of motion is towards the oppo-
site extremity, the resolved components of the motions in the
direction of the line being taken when the motions are oblique ;
for evidently, in order that equilibrium of pressure may exist, or
in order that the particles in their mutual mterchange of motion
may balance each other's effects, as many particles must be
moving in any one given direction as in the opposite.

The principle involved in the movement admits, therefore, of
being illustrated in a very simple manner ; and as regards method
of illustration we are to a certain extent indebted to a paper by
Waterston, *0n the Theory of Sound;'* this paper treating
specially of the mode of propagation of waves by the air mole-
cules, whose normal motion is consi-
dered to take place in accordance with Fig. l.
the theory of Joule and Olausius. Let

¥

US suppose a line or row of spheres
1, 2, 3, &c. (Fig. 1), of which as
many at any given instant are moving
towards one extremity of the line as towards the opposite ; or we
may suppose all those spheres designated with the odd numbers
to be moving simultaneously in one direction, while those desig-
nated with the even numbers are moving simultaneously in the
opposite direction. The motion of the spheres may be supposed
to take place without resistance, and so to go on continuously;
the row of spheres being fiirther supposed as placed between two
plane surfaces A and B, from which the end ones rebound, the
whole line of spheres being thus in equilibrium and exerting by
their inapacts a pressure tending to separate the controlling surfaces
A and B. Each sphere, therefore, performs a simple reciprocating

♦ *Philoflophical Magaasine,' Jan., 1859, Sup^, to ^Ql^i^a,

26

movement within the space bounded by the dotted lines in the
diagram, the spheres continually coming into collision or rebound-
ing from each other ; one half their number, represented by the
odd numbers (i. e. one half the total mass of matter forming the
row of spheres), moving simultaneously in one direction, during
the time that the other half, marked with the even numbers,
moves in the reverse direction, the whole line of spheres being
thus in perfect equilibrium, and not tending bodily as a whole
to move in any particular direction, but simply tending to open
out or expand, and to separate the controlling surfaces A and B.

This it may be observed is the only mode of motion possible
to the spheres by which equilibrium can be maintained ; in fact,
this constitutes in principle the only mode of motion possible to
matter by which it can be in rapid motion, and yet, regarded as a
whole, can maintain a fixed position ; for an oscillatory movement
is the only means by which a mass can be in motion and yet not
deviate from a given spot ; and the movement of an equal quan-
tity of the matter in any two opposite directions is the only means
by which equilibrium can be maintained, the two moving portions
thus precisely balancing each other's efiects ; this being the case
with particles of an aeriform medium, which move in such a way
that at any given instant along any imaginary straight line in the

medium there are on the whole

(l)Al"**!*«"i"»*''**'|R ^® ma^y particles moving in one
^' l^i^i^l^l direction as in the opposite.

In the diagram, i. n. m.
.V I ! ; ! Id ^^* ^' °^^y serve to represent
(11) AJ ?!^ i j!4 P different phases of the movement.

It is, of coiuBe, clear that in the

I; J ; I actual fact the motions and col-
T i T i T i T r ^^®^?^® ^^ *^® particles of an
• ' ' • aeriform medium would be ob-

^. I • I lique and irregular along such an
» ! ^ • Jb imaginary line; but since the
^ ! ^!*^ 1 '^l particles maintain an equilibrium
I, I , . by their collisions when a sufB-
"•* ! "*•" ! "•^ i *•" IB ci®^* number are taken into ac-
^ \ ^ \ ^ \ "^ I coimt, the principle involved in

the movement cannot therefore
be at all aflfected by making the motions regular ; and the mode
of illustration, as shown in the diagram, wUl therefore serve to
give a perfectly just idea of the principle involved, and to show
the mode in which waves are propagated.

38. We will suppose now that a forward and backward motion
is communicated to the plane A, in the form of a vibratory move-
]nent ; also the line of spheres may be supposed to be extended
indefinitely from the plane A, the movement of vibration of the
plane being also supposed slow, compared with iJie normal velocity

27

of the spheres. In that case the sphere 1 would strike against the
plane A a number of times during one forward movement or
semivibration of the plane. On the commencement of the first
forward motion of the plane, the plane moving towards the
sphere 1, the latter receives a small increment of velocity, which it
transfers at the collision to sphere 2, the two spheres simply
exchanging velocities. The sphere 1, therefore, returns to the
plane with its original normal velocity unchanged, and receives a
second similar increment of velocity from the plane, which it
again transfers, &c. The sphere 2 at once transfers to sphere 3
the increment of velocity received from sphere 1, the sphere 2
returning with its normal velocity to repeat the process. In this
way, during one forward movement or semivibration of the plane
A, a series of small, successive increments of velocity are propa-
gated in the form of a pulse, by exchange of motion along the
line of spheres, the velocitv of transmission of the pulse being
that of the spheres themselves, or the velocity of transmission is
equal to the normal velocity of the spheres. The length of this
pulse or semiwave evidently must depend on the time taken by
the plane to complete a semivibration, or wave length is pro-
portional to vibrating period. The wave length will aim evidently
depend on the normal velocity of the spheres.

These points are practically illustrated in the case of gases, or
aeriform media generally, the different rates of transmission of
waves (waves of sound, for example) by various gases being
proportional to the different normal speeds of the component
molecules of the gases. The molecules of hydrogen have a
normal speed about four times greater than the molecules of air,
and waves (such as waves of sound) are transmitted by hydrogen
at a speed about four times greater than in the case of air ; also a
wave due to a given vibrating period, when generated in hydrogen,
is about four times longer than when generated in air.

39. Ketuming to our illustrative case. The pulse due to the
forward motion of the plane A being made up of a succession of
spheres, moving (at the time of passage of the pulse) with a
velocity slightly in excess of the normal velocity of the spheres
forming the advanced portion of the line, this portion of the
wave, or the spheres forming it, would therefore be slightly
shifted forwards, producing a ** condensation."

The plane comes to rest gradually before changing the
direction of its motion ; and the opposite movement is also com-
menced gradually, the motion of the plane being therefore almost
nothing for a short interval, so that the first portion of the wave
is separated from the second by a succession of spheres whose
normal velocities have not been appreciabljr changed, an effect
corresponding to the normal mass of air which separates the two
portions of a wave of sound.

By the backward movement of the plane at the next oiox&i-

28

vibration^ a series of small decrements of velocity, forming the
second half of the wave, is transmitted in the same manner along
the line of spheres ; and the velocity of the spheres at the instant
when this portion of the wave passes them, being slightly less than
the normal velocity of the adjacent spheres, this half of the wave,
or the spheres forming it, are therefore shifted backwards in
relation to the advanced portion of the wave, an opening ont of
the line of spheres, or a " rarefaction," being the resnlt It is
clear that in the actual fact in the case of an aeriform medium,
since the motions of the particles take place also obliquely to the
line of propagation of the wave, the rate of propagation cannot
therefore equal the normal speed of the particles, but must be to
a certain degree slower. This, however, does not aflfect in the
least the principle involved, and, accordingly, the above mode of
illustration will serve to convey a perfectly just idea of the mode
of the normal motion of the component particles of an aeriform
medium, and the physical means by which through this mode of
motion " waves," or any changes of velocity experienced by the
particles, are propagated to a distance along the medium.

SECTION m.

40. Ths Phenomena of ^^ Attraction*^ and ** Bepulsion** — In
returning to the consideration of the phenomena of " attraction "
and ** repulsion," we may first give some quotations from some
papers contained in the 'Philosophical Magazine' (November,
1870; June, 1871), descriptive of experiments with masses of
matter vibrating in air (tuning-forks, &c.), these experimental
results being illustrative of the power of vibrating masses to
disturb the equilibrium of pressure of the intervening medium^
attended by the effects of attraction and repulsion.

These phenomena appear to have been experimentally investi-
gated at about the same time, and independently, by Guthrie,
Uuyot, and Schellbach. In these papers numerous interesting
experiments are detailed relative to the attraction and repulsion
of various freely suspended substances, by tuning-forks ana other
vibrating bodies, and we may give the following quotations, as
showing the striking and distinct character of the results obtained.
We give, first, some quotations illustrative of the experimental
results obtained by Mr. F. Guthrie.*

41. Experiment 7. — "To one end of a splinter of wood 0*5
metre long, a card • 08 metre square was fastened in such a way
that the pane of the card was vertical, and contained in the line

♦ • PhU. Mag.; Nov., 1870.

29

of the splinter. The whole was hung from a fibre of unspun silk,
and counterpoised. The tuning-fork was set in vibration, and was
brought towards the card in three relative positions. In all three
cases the card moved towards the fork. The rate at which the
card moved was greatest when the fork was sounding loudest. In
all three cases it was possible to draw the card from a distance
of 0*05 metre at least.

To test the reciproeity of the motive tendency the following
experiment was tried : Experiment 8. — " The tuning-fork was
fastened to the end of a rod 1 metre long ; the end of the rod was
counterpoised, and the whole was hung from a silk tape." The
description adds, that when a card was held near the vibrating
suspended fork, the fork moved towards the card; this being
evidently the exact converse of the previous experiment. The
following quotation illustrates this point further : Experiment 9. —
" Further, instead of a card, a second fork B was set in vibration
and brought into the neighbourhood of the vibrating suspended
fork A. In every case the suspended fork approached the station-
ary one." *' Hence, to whatever cause the approach is due, the
action is mutual." The following few quotations serve to show
the distinct character of results obtained by M. Schellbach.* When
a sounding box was used, the description adds, "The above-men-
tioned sounding box distinctly attracted and brought into contact
with itself easily movable metallic sheets and balls, even such as
weighed 120 grammes, and were at a distance of 8 centimetres."
Another experiment was as follows: "A ball, weighing three
kilogrammes, hanging from a silk thread 2 metres in length, could
be set in visible vibration when the fork was stroked isochronously
with the pendulum vibration."

The following account of an experiment is of interest, as
pointing to the analogy between the vibrating tuning-fork put in
resonance by waves of sound (air waves), and the vibrating
molecule put in " resonance," so to speak, by waves of heat (ether
waves) : " These and the previously mentioned phenomena (i. e.
phenomena of attraction) were also produced, although to a less
degree, when a tuning-fork was set in vibration by means of a
second fork in unison with it. Actions were still visible when the
distance between the forks was one metre."

42. These striking experimental facts carry their practical
deductions with them, and in their application to molecules
vibrating in the ether, there are only two conditions, important in
a mechanical point of view, which require to be satisfied, viz. first,
the existence of an ether pressure of a value commensurate with
the high static value of the efiects observed in the case of vibra-
ting molecules ; and, secondly, the vibrations of molecules must
take place with an energy commensurate with the energy of the
effects. The first of these two conditions heis been already con-

♦ *Phil.Mag.,' June, 1871,

30

sidered and disposed of; for it is not only possible to show that an
adequate ether pressure commensurate with the eflTects is prac-
ticable, but the observed speed of a wave of light, as pointing to
the high normal speed of the ether particles, renders the exist-
ence of a forcible pressure a necessity, although every allowance
be made for the low density of the ether. The existence of this
forcible pressure is evidently a necessary mechanical condition to
the eflTects, for the pressure of the agent must, at least, reach the
highest static value of the force with which the vibrating masses
or molecules are urged together. Thus, in the case of the air, for
example, the attraction of vibrating masses, such as for instance
the mutual attraction of two vibrating tuning-forks, however great
the vibrating energy, could never exceed or indeed reach the
static value of 15 lb. per square inch of surface acted against, this
being the limit of the normal air pressure, the approach of the
forks being due to the excess of the normal air pressure above the
reduced air pressure between the forks, due to the vibrations.
In the case of the ether, therefore, where the observed eflTects in
the case of vibrating molecules attain a static value far surpassing
that possible in air, the existence of a forcible ether pressure is,
therefore, an absolutely essential physical condition.

The second of the two physical conditions requiring to be
satisfied, viz. the existence of a degree of vibrating energy in the
case of molecules, commensurate with the observed energy of the
phenomena of attraction and repulsion, we shall now proceed to
consider more particularly.

48. Absolute Mechanical Value of the Molecular Vibrations. — In
regard to the normal *' temperature " (normal degree of molecular
motion) possessed by the various materials on the earth's surface,
one is perhaps liable to overlook, or at least not to appreciate
fully, the fact that the absolute mechanical value of this molecular
motion is extremely high. A general equilibrium of temperature
tends to be maintained, and only changes of temperature (which
are extremely small compared with the absolute temperature) can
aflTect the senses, so that the absolute energy of the molecular
vibrations (the absolute " temperature ") might possess any value,
however high, and yet the senses would be wholly unable to detect
the fact of the existence of this energy, and only would the intensity
of the molecular energy actually existing become apparent in the
most striking manner if in any one instance this motion were to
cease. From the fact, however, that a general equilibrium of
molecular motion is maintained on all sides, its existence neces-
sarily eludes notice, and there is therefore a tendency for the
absolute mechanical value of these molecular motions and their
practical teaching to escape a due appreciation.

44. In order to form a just estimate of the energy of the eflTects
of attraction and repulsion capable of being produced by vibrating
molecules, it is necessary to form an adequate realization of the

31

absolute mechanical value of these vibrations, and the mechanical
value of the vibrations of molecules must then be compared with
the mechanical value of the vibrations of masses, such as the
tuning-forks, &c., by which the observed effects of attraction,
already described, were produced.

It may be safely assumed that the mechanical value of the
vibrations of the tuning-forks, in the experiments referred to,
was not greater than that which would be produced by a blow
upon the prong, due to a fall of the fork through 10 to 20 feet,
and thereby striking its prong against a hard surface. This is
merely intended to give a rough idea of the small mechanical
value of the vibrations of the forks (merely stroked with a violin
bow) which produced the distinct effects of attraction described ;
the actual mechanical value of the vibrations being probably less
than the above estimate.

We will now endeavour to investigate, approximately, the actual
mechanical value of the vibrations of the small component parts
of the fork, which are termed " molecules," to the vibrations of
which (by the waves generated in the ether) the mutual ** cohesion"
of the molecules is to be referred. We will suppose the fork to
be at the normal temperature of 60° Fahr., this representing an
absolute temperature of 519 of Fahrenheit's degrees, reckoned from
the absolute zero. The addition of 1° Fahr. to the temperature
of a mass of water represents, as is known, an addition to the
energy of the motion of its molecules, which would be competent
to project the mass of water (i. e. each molecule) to a height of
772 feet, or is equivalent, in mechanical value, to the energy
developed at the impact of the mass after a fall from the above
height. The specific heat of iron or steel being one tenth that of
water, the addition, therefore, of 1° Fahr. to the temperature of a
mass of steel represents an addition of energy equal to that
developed at the collision of the mass after a fall of 77*2
feet.

The actual value of the vibrating energy possessed by the
molecules of the steel fork at normal temperature is, therefore,
equal to the energy developed at the collision after a fall of the
fork through 519 X 77*2 feet, about 7^ miles, this corresponding
to a velocity of 1600 feet per second. If, therefore, we imagine
the molecules of the fork to be without vibratory motion (i. e.
without " heat," or at the " absolute zero ") at the commencement
of the fall through the above height, and that the work of the
collision were entirely expended in developing vibratory motion
in the molecules of the fork (raising the " temperature " of the
fork), then the fork would be at 60° Fahr. after the collision.
The vibratory motion of the molecules of the fork at normal tem-
perature (60 Fahr.) therefore takes place with such an energy,
that the vibratory motion if entirely utilized would be competent
to project the molecules to a height of about seven. ixv\\a%^ ^^ \r»

32

project the molecules of the fork apart at a speed in excess of that
of a bullet.

45. If, therefore, the molecular vibrations take place with this
intense energy, then surely the forcible effects of attraction
observed in the case of molecules are only consistent with the
high intensity of the vibrating energy possessed by them. If the
feeble vibrations of a tuning-fork be competent to produce dis-
tinct effects of attraction, then if only due weight be given to the
incomparably more intense vibrating energy of molecules which
derive their energies from the powerful dynamic agency of the
sun, then the power of the molecular attractions reconciles itself
with ordinary mechanical principles, as powerful effects are the
inevitable result of powerful causes. It may also be noted that
the separating distances of the molecules of substances being
extremely small, the energy of the wave motion set up in the
ether is but little reduced by distance, also on account of the
great subdivision characterizing the molecular state, the extent of
surface exposed to the action of these waves must be exceedingly
large.

46. These considerations have a general application, and the
remarkable fact of the extreme variety of vibrating period ob-
served in the case of molecules, the observation of which has
formed a special study vnth the spectroscope, has a definite object,
viz. that 01 fixing the " affinity," or special " combining power," of
the molecule, for it is clear that if the movements of molecules
comprised under the phenomena of " attraction and repulsion," be
dependent on the molecular vibrations as a physical cause, then
so important a change as a change of wave period, and indeed any
change whatever affecting these vibrations, must have its influ-
ence on the effects of these vibrations, L e. on the movements and
deportment of molecules ; an influence on the physical cause
being necessarily attended by an influence on the physical effect,
the vibrations supporting each other or interfering more or less as
the wave period changes.

The vast variety of wave period observed points all the more
convincingly to the fitness of the molecular vibrations as the
regulator of the complex and varied effects exhibited in the move-
ments of molecules in ** chemical action," or those diverse mole-
cular movements which belong to the science of chemistry, the
remarkable diversity in the character of the })hysical cause pro-
ducing naturally a remarkable diversity in the eflects.

The terms " attraction " and " repulsion " serve as convenient
terms to denote the direction of the motion or tendency to motion
exhibited by masses or molecules due to a disturbance of the
equilibrium of the dynamic action of the particles of the sur-
rounding medium. The term " repulsic n " gives some idea of the
mode of action. Possibly a term less vague than ** attraction
might be used with advantage : *' attraction " and " repulsion

99
99

33

being simply impulsion in opposite directions of the mass or mole-
cule under the dynamic action of the particles of the medium.

47. In viewing the phenomena of the movements and mutual
actions of molecules as a physical problem, it really is not con-
ceivable that anything could be moie admirably adapted to
produce the effects than the vibrations of the molecules, which
also by variation of wave period are capable of building up the
almost endless variety of chemical compounds. In fact, if the
question be fairly examined into, there exists no other conceiv-
able process by which one mass or molecule of matter could move
or act upon another mass or molecule placed at a distance than
by means of vibration. For in the first place, in order for a mass
of matter to be capable of moving, or ph) sically affecting a second
mass placed at a distance without approaching it, the mass must
have a motion of some kind so as to be capable of disturbing the
surrounding medium, which forms the only physical connection
between the masses. Secondly, since the mass or molecule in
acting upon the second molecule maintains a fixed position, it
follows tnat the motion of the molecule must take place in such
a way that the molecule can maintain a fixed position, and never-
theless can disturb the surrounding medium. Now, a vibratory
motion of the molecule constitutes the only conceivable means of
satisfying these conditions, as by this form of motion the molecule
can retain a fixed position by oscillating about a fixed point, and
yet can disturb the surrounding medium by its motion. Hence,
in a mechanical point of view, nothing can be more obvious or to
the purpose than the vibratory motion of matter so constantly
presenting itself in physical phenomena.

48. A molecule of matter surrounded by the ether cannot
possibly be in motion without disturbing the ether, and thereby
giving up or dissipating continually its motion in the surrounding
ether. This disturbance of the ether by the motion of molecules
is illustrated by the waves emitted by the molecules of substances,
and the attendant loss or dissipation of the motion of the mole-
cules is exemplified by the cooling (loss of molecular motion) of
heated substances when suspended in the free ether. It follows,
therefore, from this that the motion of molecules which is being
continually dissipated in the ether must be sustained by some
external source of motion, or otherwise the motion of molecules
would soon cease. This is illustrated by the known fact that the
motion of molecules is sustained by the sun, it being an important
fact to observe that the character of the sustaining motion is a
vibrcUory or wave motion traversing the ether.

The fact of the special character of the motion of molecules
being a vibratory motion is therefore only an illustration of the
simple mechanical principle that the motion of molecules must
necessarily be that form oi motion which admits of being sustained
by the action of a vibratory motion traversing the surrounding ether.

34

49. Thus the vibrations or " resonance " of masses by the
sustaining action of air waves (such as waves of sound) and the
vibrations, "resonance** — so to speak — of the smaller masses
(" molecules ") by the sustaining action of ether waves (the waves
of heat) are in perfect analogy with each other : and in the same
way a resonant mass and a '* resonant " molecule (as proved by the
spectroscope) is sustained by ("absorbs") a motion of the same
character (same wave period) as it emits.

All physical effects being effects of motion, and since vibratory
motion constitutes one of the fundamental forms of motion, it
would be a thing to be expected beforehand that the general
phenomena of vibratory motion, including the production of
stationary vibrations in the intervening medium by the reflection
of the waves from masses and molecules, would have a most
important bearing on all branches of physical science, and have a
most influential part to play in physical phenomena.

50. The Static and Dynamic Effects of the Ether, — It would
appear d priori natural and even necessary that certain " static "
effects, or effects of pressure, should exist in the case of that
influential agent the ether, just as static effects of pressure are
apparent in the case of the air. The phenomena of " cohesion " or
the general phenomena of the aggregation of molecules, including
the physical conditions governing the equilibrium of molecules,
would come under the *' static" effects of the ether; while the
phenomena of the motions of molecules, such as the phenomena of
chemical action, would come under the dynamic effects of the ether.

SECTION IV.

51. Mode of the Production of Motion through Vibration. — We
shall now endeavour to investigate the mode or physical process
by which motion is produced through vibration; and that not
specially with the view to add proof to the circumstance that
motion can be produced through vibration, this being already an
observed fact in certain known experimental cases : just as, for
example, we might investigate the mode or physical process by
which a vibrating tuning-fork attracts a piece of card, without any
view to add proof to the observed fact that the vibration of the
fork can produce the attraction.

We have referred to the observed cooling of a heated substance
in the free ether as a direct illustration of the fact that the motion
of the molecules is being given up to the ether, and that, therefore,
the emitted waves must on the whole contain an excess or surplus
of energy, this surplus of energy representing precisely that lost

35

by the molecules of the substance in the act of cooling down. We
have now, therefore, to consider the mode or physical process
by which the vibratory motion of a mass or molecule communicates
a certain excess or surplus of energy to the surrounding medium.

As a simple and generally applicable example, we may take
the case of a tuning-fork vibrating in air. Then considering any
one of the emitted waves : the physical disturbance of the air,
termed " a wave," is of such a nature that the component molecules
of the one half of the portion of air forming the wave have received
an increment of velocity, the component molecules of the other
half of the portion of air forming the wave having suffered an
equal decrement of velocity ; also the amount of condensation in
the one half of the wave is the equivalent of the amount of rarefac-
tion in the other half. An air wave may therefore be properly
regarded as a mass of air in which the uniformity of the distribu-
tion of the molecules and of their velocity has been disturbed in
such a way that a transference of matter and of velocity has taken
place from one half the mass of air to the other half.

52. But it may now be shown as an important point that
although the increments of velocity equal the decrements, that
nevertheless the special physical conditions under which these incre-
ments and decrements are experienced are such that a certain excess
or surplus of motion is imparted to the air, or exists in the wave.
This deduction follows from the consideration tliat the portion of
air whose molecules receive an increment of velocity is condensed
in the act of receiving it, owing to the advance of the vibrating
mass (or prong) towards the portion of air which receives the
increment of velocity ; while, on the other hand, the portion of
air whose molecules suffer a decrement of velocity is rarefied in
the act of losing it, owing to the recession of the vibrating mass
from this portion of air; so that, therefore, although the incre-
ments and decrements of velocity experienced by the molecules
situated in the corresponding halves of the wave are equal, yet
from the effect of the condensations and rarefactions, the number
of air molecules which receive an increment of velocity is greater
than the number which suffer an equal decrement, so that a certain
excess of motion exists in the mass of air forming the wave, or the
vibrating fork therefore imparts a certain surplus or excess of
motion to the surrounding air. The quantity of air which thus in
each wave receives an increment of motion for which there is no
corresponding decrement, is represented by the difference in mass
between the condensed and rarefied half of the wave. Since this
difference in mass between the condensed and rarefied half of the
wave, i.e. the condensations and rarefactions increase with the
vibrating energy of the fork, and also the increments of velocity
themselves increase ; it follows, therefore, that the excess or surplus
of energy imparted by a vibrating mass to the surrounding medium
must increase in a rapid ratio with the vibrating energy. This coii-

36

sideration would have its special application in the case of mole-
cules where the vibrating energy is known to attain a high
intensity.

53. Secondly, it may be shown that an excess of energy is
imparted to the surrounding medium by a vibrating mass or
molecule, due to a second separate physical cause, which we shall
now consider. We have observed that the speciality of a vibrating
movement is to affect the normal velocity of the component par-
ticles of the medium in such a way that equal increments and
decrements of velocity are experienced.

But it is an important principle to observe, that when masses
of matter experience equal increments and decrements of velocity
so that the mean velocity remains unaltered, that, nevertheless,
the energy being as the square of the velocity, the value for the
energy does not remain unaltered. Thus, if we take the case of
two equal masses having equal velocities, which we may express
by V, the energy in each case being expressed by V^ and the
total energy therefore by 2 V^. If now we suppose one of the
masses to receive an increment of velocity v, its velocity therefore
becoming Y+v, the other mass experiencing an equal decrement
of velocity, its velocity becoming V — v; then although the mean
value for velocity has remained unchanged, yet the value for
energy has by no means remained unchanged, for the energy of
each mass being as the square of its velocity, the total energy now
becomes (V + v)^ + (V - v)^ = 2 V^ + 2 v\ Now the value for
the total energy before this change of velocity took place was only
2 V^. The total energy has therefore, by merely changing the
velocities by equal amounts (so as not to affect the mean velocity),
received a notable increase represented by the amount 2 v^. This
is an important point, on account of the direct and practical bear-
ing which it has on the phenomena of vibratory motion; the
above indicating that the change of the velocities of the component
particles of the medium by equal amounts, which it is the special
function of a vibratory motion of matter to effect, is itself a airect
cause whereby a certain excess or surplus of energy is communi-
cated to the medium.

54. Hence, taking this cause into account, together with the
one previously considered, it may be observed that there exist two
separate influential physical causes by whose action the vibrations
of masses or molecules are in all cases attended by the communi-
cation of a certain excess or swrjplus of energy to the surrounding
medium.

The deduction that by the vibrations of masses or molecules a
surplus of energy is imparted to the surrounding medium, is
clearly of direct and practical importance as regards the phe-
nomena of " attraction," &c., for the communication of energy to
the component particles of a medium implies necessarily, under
certain conditions, an expansion or rarefaction of the medium, and

37

a rarefaction of the medium is the very condition required for an
" attraction."

The observed fact of the resistance offered by an aeriform medium
to the passage of masses, or indeed the simple observation of the
resistance encountered in waving a fan, constitute other illustra-
tions of the fact that the vibrations of masses are attended by the
communication of a surplus of energy to the surrounding medium.

55. Since the presence of other vibrating masses cannot
possibly influence the amount of energy imparted by a vibrating
mass to the surrounding medium, it follows that a substance at
normal temperature is losing as much heat or is imparting as
much energy to the surrounding ether as if the substance were
completely isolated, or as if everything around were at the absolute
zero of temperature, only the substance under normal conditions
maintains its temperature unchanged, from the fact that the sub-
stance is receiving as much heat from surrounding objects as it
expends. • Taking normal temperature at 60° Tahr., then this repre-
sents an absolute temperature of 519 of Fahrenheit's degrees,
reckoned from the absolute zero.

Since the waves developed in the ether by substances at
normal temperature do not affect the senses, on account of the
perfect state of equilibrium of motion which exists, or only an
increase of temperature above the normal can affect the senses ; in
order, therefore, to be capable of forming a just idea of the amount
of energy which is being given up to the ether continually by
substances at normal temperature, it will only be necessary to sup-
pose the temperature raised as much above the normal as the
normal temperature is above the absolute zero, in which case
substances would be giving up to the ether an addition of energy
precisely equal to the energy which they were giving up at normal
temperature. Accordingly, normal temperature being taken at
60° Fahr., we have therefore to add 519° to this temperature, giving
579° Fahr. A substance therefore at the burning temperature of
579° Fahr. has only received an addition of vibrating energy which
is equal to that which it possessed at normal temperature, and
which its molecules were actually imparting to the ether without
affecting the senses. From this it may be judged what an amount
of energy is being continually given up to the ether by the mole-
cules of substances at normal temperature. If we take the case of
water, which is a good radiator, and suppose a quantity repre-
senting one pound to be spread out into a layer or film, so that the
vibratory motion of the molecules can be freely imparted to the
ether, the area of the film being supposed such that the mass
of water by radiation and absorption exchanges an amount of heat
represented by only seven-tenths of a degree Fahr. per second, then
it may be computed that the vibrating molecules of the pound of
water at normal temperature are working up to about one-horse
power in the amount of energy being continually given vsl^ ^s^ NJ^sa

38

ether. These considerations have their direct application as
regards the intensity of the static and dynamic eflfects capable of
being produced by the vibrations of molecules.

56. In dealing with the question as to the mode in which
motion is produced by vibration, we will suppose a special illustra-
tive case as serving best to put the
^^^* ^* subject in its clearest light. Let us

> , 41 < I suppose a cylinder or tube (Fig. 2)

containing air, a piston fitting into
one end of the tube, the other end being closed. The piston placed
just within the tube is supposed to admit of being put in rapid
vibration, the limits of oscillation of the piston being supposed so
small compared with the length of the tube that the influence of
the change of volume of the enclosed air does not come into
account. Then it follows necessarily from the previous consider-
ations that a certain surplus of energy is imparted to the enclosed
column of air by the vibrations of the piston. But since it is
impossible to impart energy to the molecules pf a mass of air
without that mass tending to dilate, it follows that the confined
column of air will, under the action of the vibrating piston, tend
to expand and thus exert a pressure tending to drive away or repel
the base of the cylinder and piston, and to expand the cylinder
laterally, the energy of the effect being only limited by the energy
with which the piston can be made to vibrate or oscillate. Since
the surplus of motion imparted to the molecules of the air column
accumulates at every stroke of the piston, it follows that the
pressure would increase continually by simply continuing, even at
a slow speed, the vibration of the piston, if it were not for the fact
that an increase of the translator^ motion of the air molecules is
necessarily accompanied by an increase of the vibratory motion
(heat) of the molecules, which form of motion can communicate
itself to the molecules forming the cylinder, and thus be conducted
away or dissipated, a limit being thus set to the rise of pressure
which is thus made dependent on the energy of vibration of the
piston. In the actual state of the case, therefore, the inference
follows that the pressure will only rise until a stage is reached at
which the amount of heat conducted away or dissipated through
the cylinder is the precise mechanical equivalent of the work
done in maintaining the oscillation of the piston, deducting
therefrom the small unavoidable resistances due to the friction of
the piston against the tube, &c.

57. If the sides of the cylinder were supposed to be partly
formed of some elastic substance capable of distension, then the
pressure exerted by the enclosed air would be necessarily followed
by an expansion of the enclosing envelope, and this by a
rarefaction of the enclosed air, the degree of rarefaction thus
attainable being only limited by the degree of vibrating energy
capable of being imparted to the piston. JFrom these considerations

39

we may deduce the important general conclusion that matter in
stationary vibration tends forcibly to dilate and displace anything
which hinders its free expansion.

58. We will now consider more closely the mode of vibration
of the air column in such a case. It is evident that the air column
would be thrown into stationary vibration by the reflection of the
pulses of air from the base of the cylinder. We will first suppose,
for simplicity, that the period of vibration communicated to the
piston corresponds with the vibrating period of the air column,
the air column in such a case vibrating as a whole in synchronism
with the piston.

We then observe that the increments of velocity given to the
air molecules are reflected from the base of the cylinder, back
upon the piston, and in this case the time taken for a complete
reflection is that of a single vibration, so that in this case an
additional increment of velocity is given to the molecules of the
air column at every stroke of the piston, which, if it were not
dissipated in heat, would cause a continuous rise of pressure, and a
continually increasing efibrt of the air to expand and rarefy
itself.

59. A vibratory motion of matter would thus, in fact, appear to
be one of the best possible mechanical means of communicating
motion to the particles of a medium, and thereby causing the
medium to expand forcibly and rarefy itself. In fact, when the
physical conditions of the case are analyzed, we have the particles
of the medium impinging continually with their normal velocity
against a given mass of matter, so that it is only necessary to put
this mass of matter in motion in order to communicate motion to
these particles, and a vibratory motion is the form of motion
specially adapted for this object, since by this form of motion the
mass can communicate, continually, motion to the particles of the
medium, and yet the mass can maintain a fixed position. Hence
a vibratory motion of matter may be justly said to constitute the
best-adapted mechanical means of accumulating motion in the par-
ticles of an aeriform medium, and thereby causing, under suitable
conditions, a forcible rarefaction of the medium, this rarefaction of
the medium being the physical condition required for an
** attraction."

60. It may be further observed as an important point, as
generally characteristic of the stationary vibration of a medium,
that the motion of the oscillating air column, as in the present
illustrative case, takes place in such a way that the condensed
portion of the reflected wave meets the oscillating mass (piston)
at its advance, while the rarefied portion of the wave meets the
piston at its recession, so that for this special cause the incre-
ments of velocity are given at each impulse to a greater number
of air molecules than would be the fact if the air column were
not already in stationary vibration, so that for this a^jeciaL oaRSfo

40

the work done by the vibrating piston upon the air column is
augmented. The experiment of holding a vibrating tuning-fork
over a resonance jar, when the fork loses its motion much more
rapidly than under normal conditions, serves to illustrate the
fact of the greater amount of work done by a vibrating mass
upon the air when the air is in stationary vibration.

61. We will now, for further illustration, imagine the vibra-
ting period of the piston to correspond with the vibrating period
of the half column. Then the air column would, as is known

under these conditions, break up into

^®-^- two oscillating halves or segments

_♦ — 41 .. I > "n (Fig. 3), vibrating in synchronism with

the piston, the two halves of the co-
lamn rebouuding from each other at the centre of the cylinder,
and then rebounding simultaneously from the piston and the
base of the cylinder. This case serves to illustrate well the
expansive action attendant on the oscillations of the air column,
the impacts of the halves of the column tending to drive out
the ends of the cylinder; an^l since aeriform media propagate
pressure equally in all directions, the sides of the cylinder must
tend to bulge outwards, so that if the cylinder were partly com-
posed of some elastic material it would expand laterally, this
expansion being necessarily followed by a rarefaction of the en-
closed air column, the degree of rarefaction thus attainable being
only dependent, on the vibrating energy of the piston. I'his
illustrative case serves to convey a mechanical idea of the mode
in which matter in stationary vibration tends to expand in eveiy
direction and displace that which confines it. If the character of
the motion constituting a stationary vibration of matter be consi-
dered, as in the present case, it may be noted that each half of the
air column simply performs a movement of oscillation between the
centre and ends of the cylinder, so that each oscillating half of
the column might be supposed replaced by an elastic sphere, which
performs a reciprocating movement analogous to that of the half
column, the two spheres rebounding from each other at the centre
of the cylinder, and then rebounding simultaneously from the
piston and base of the cylinder, the two spheres thus performing
motions precisely analogous to those previously performed by the
halves of the air column, the motion accumulating at each stroke
of the piston, and the two spheres tending by their impacts to
repel the ends of the cylinder in the same way as was the case
with the oscillations of the two air ma&ses.

62. If the piston were supposed to be made to oscillate to a
more rapid period, then the air column would, as is known, divide
into a greater number of oscillating parts or segments (Fig. 4), the
principle involved in the motion being, however, precisely the same
as in the case of two segments or in the case when the column
osc}}]ato8 as a whole. The segments into which an air column

41

divides under the influence of vibration are well shown by the
known experiment of putting a glass tube, having dust scattered
in its interior, into stationary vibration by friction, when the
enclosed air column being thus thrown into stationary vibration,
the dust divides into a series of segments showing the corre-
sponding division of the vibrating air column.

Fig. 4. Pio. 5.

• ••II

] * m > m' t ^m t m' *

• • • I •

We may, therefore, again suppose the oscillating segments of
the column (Fig. 4) to be replaced by elastic spheres (Fig. 5),
each of which performs the reciprocating movement of the corre-
sponding segment. Every alternate sphere, such as all those
marked with the odd numbers, would at any given instant be
moving simultaneously in one direction, while those marked with
the even numbers move simultaneously in the reverse direction,
this being the motion corresponding to the segments of the air
column.

63. Now, it may be remarked as a point of interest that the
character of this motion of the segments of the air column, or
any column of a medium in stationary vibration, represents the
character of the normal motion of the integral particles of the
medium, when the resolved components of the motions of the in-
tegral particles of the medium in any two opposite directions are
taken ; precisely the same diagram having previously served in
treating of the motion of the integral particles of an aeriform
medium. It will be evident that this must be so, or the principle
of the motion must be the same in both cases, since in both cases
the character of the motion must be such that the column can be
in equilibrium and maintain as a whole a fixed position in space,
and, as before referred to, this is the only possible form of motion
which satisfies these conditions, the motion in both cases taking
place in such a way that as much matter at any given instant is
moving in one direction as in the opposite. Thus it will be ob-
served that the segments into which the column is divided move
in such a way that the same quantity of matter is moving at any
given instant in one direction as in the opposite, the sum of
the segments moving in either direction representing half the
column. A consideration of this analogy in the form of motion
serves to show in a striking light the expansive action attendant
on a stationary vibration of matter, or the motion of the oscillating
masses of air into which the column is broken up tends to expand
the column in all directions, or to dislocate and throw asunder its
parts, just as the normal motion of the integral molecules of the
column tends to expand it in all directions ; indeed, the effect of
throwing the air column into stationary vibration is sim^l^ tcs

42

superadd to its own molecular motion a palpable mass motion of
its parts. This tendency of matter when in stationary vibration
to expand or dislocate its parts is well shown by the experiment
of throwing a glass tube into forcible stationary vibration by fric-
tion, when the tube may be split into a series of rings, its vibrating
parts flying asunder. Here the expansion is resisted by the
cohesion of the glass. In the illustrative ease of the vibrating
column of air confined within the cylinder, the expansion of the
column is resisted by the external envelope or cylinder, which
consequently has to bear the pressure ; and if means were given for
the air column to expand freely, a rarefaction of the air would
be the result, the degiee of rarefaction attainable depending only
on the energy with which the column is thrown into vibration.

64. The tendency of matter in stationary vibration to dilate
and cause displacement might even be illustrated by the simple
experiment of shaking longitudinally a corked tube partly filled
with water and held horizontally, when the cork might thus be
forced out by the oscillating mass of liquid. Here the stopped
ends of the tube, when the tube is shaken longitudinally, play the
part of two oscillating pistons throwing the enclosed liquid into
vibration. It can be of no consequence, as far as the principle is
concerned, whether the matter thrown into vibration be water, air,
or the ether ; only to produce a given efiect, the speed of vibration
must of course be greater as the matter concerned is less dense.
In the above case the relatively very great density of the water
enables a perceptible eflfect to be produced even by the slow
shaking of the hand. A stationary vibration of matter is, in fact,
simply a violent shaking of the matter acted upon, which therefore
tends to expand in every direction, and drive away that which
confines it ; and if the matter in vibration be free to expand, then
a forcible rarefaction is the result.

The above considerations all lead to the general conclusion
that the method of vibration is a mechanical process eminently
adapted to disturb forcibly the equilibrium of pressure of a
medium, which may be attended by forcible movements of masses
of matter, whose positions of equilibrium are determined by the
equilibrium of pressure of the medium about them.

65. In the application of the above deductions to masses
vibrating freely in a medium, such as to the case of vibrating
molecules and free vibrating masses generally, we have only to
consider the state of the case when the envelope is wanting, such
as the case when the enclosing cylinder, or the distensible envelope
in the illustrative example is removed ; when the piston would be
oscillating freely opposite the base of the cylinder, in perfect
analogy with the prong of a vibrating tuning-fork oscillating
freely opposite a piece of card, or with two molecules vibrating in
opposition to each other.

It will he evident that the effect of removing the lateral

43

envelope will be to afford facility for the lateral expansion, and
therefore rarefaction, of the intercepted air column, or the column
of the medium intercepted between two opposed vibrating masses
(or molecules), the absence of the envelope enabling the oscillating
column of the medium to expand laterally with freedom, the
column thereby becoming rarefied.

Thus, if we take the case of a vibrating tuning-fork held in
proximity to a lightly suspended piece of card, then the incre-
ments of velocity imparted to the molecules of the column of air
intercepted between the vibrating prong and the card, accumulate
by repeated reflections between the opposing surfaces of the prong
and the card, producing a rarefaction of the air column, whereby
the excess of pressure of the air at normal density at the back of
the card coming into action, drives the card towards the prong. If
the fork be supposed to be maintained at a constant degree of
vibrating energy, then the increments of energy which, under the
action of the two physical causes before dealt with, are continually
imparted to the molecules of the intercepted air column, and which
accumulate by repeated reflections from the card and prong,
would be necessarily followed by a continually increased rarefaction
of the intercepted air colunm, were it not for the fact that a
portion of the vibrating energy of the column is dissipated
laterally into the surrounding medium, by which a fixed limit is

Eut to the rarefaction of the air column, the degree of rarefaction
eing thus made dependent on the vibrating- energy of the prong.
The same considerations apply in the case of two molecules
vibrating in opposition to each other, as in the case of any vibra-
ting masses whatever, or masses of matter which emit waves.

66. The above deductions may be stated in one general con-
clusion, viz. that the vibrations of masses or molecules of matter
are in all cases necessarily attended by a rarefaction or displace-
ment of the intervening medium : this conclusion holding, however
distant the masses may be from each other, or however feeble the
vibrations; the intensity of the effect becoming greater by an
increased proximity of the masses, or by an increase of their
vibrating energy.

SECTION V.

67. The Physical Conditions of the Equilibrium of Molecules, —
In proceeding to consider the physical conditions governing the
equilibrium of molecules, it may be stated, first, that the equilibrium
of a molecule of matter depends on the equilibrium of pressure of
the medium about it.

44

We have observed that a vibratory movement of matter, under
such conditions that the waves are reflected and thereby stationary
vibrations are formed in the medium, is well qualified to disturb
the equilibrium of pressure of the medium. If we suppose the
imaginary case of a vibrating molecule of matter completely
isolated, then stationary vibrations could not be formed in the
medium, the equilibrium of pressure of the medium about the
molecule could not be disturbed, and the molecule would be in
equilibrium. But if we suppose a second molecule placed in
proximity, then the medium about the molecule is specially
disturbed at that side where the second molecule is situated, due
to the formation of stationary vibrations in the medium intervening
between the molecules by mutual reflection of the waves, a rare-
faction of the inteicepted vibratino; column of the medium which
abuts against the opposed molecules being the result. The con-
dition of equilibrium of the molecules will therefore depend upon
the fact whether the pressure of the intervening vibrating ether
column is greater than, equal to, or less than the ether pressure at
the remote sides of the molecules, where the normal ether pressure
exists ; the molecules being driven in the one direction or in the
opposite, or remaining in equilibrium, according to the relation of
these two pressures.

Now, the rarefaction which attends the stationary vibration of
the intervening ether column would, by reducing the ether density,
i. e. by reducing the number of ether particles which impinge
against the sides of the molecules which oppose each other (i. e.
the side of each molecule where the vibrating column terminates),
tend to cause a mutual approach of the molecules under the
action of the superior number of ether particles which impinge
against the remote sides of the two molecules where the ether
density possesses its normal value, this physical effect corresponding
to an *' attraction."

On the other hand, the direct action of the pulsations of the
vibrating ether column, or the direct action of the increments of
energy given to the particles of the column, would, considered by
itself alone, tend to propel the molecules farther apart, a physical
efl'ect corresponding to a " repulsion."

These are, therefore, the two opposing physical influences which
determine the position of equilibrium of each molecule, each mole-
cule being driven in the one direction or in the other, or remaining
in equilibrium, according as the direct influence of the pulsations
of the intercepted ether column or the indirect influence of the
rarefaction attendant on these pulsations attains the upper hand,
or the two opposing influences become equal.

68. It follows, therefore, that two molecules can only be in equi-
librium under those special physical conditions when by a special
adjustment of distance and vibrating energy these two opposing
physical iuRiiencea happen precisely to counteract each other ; the

45

molecules being urged in the one direction, or in the opposite,
" attracted," or " repelled," according to which influence pre-
dominates under the existing physical conditions.

69. When the separating distance of two molecules is made to
vary, this change of distance is necessarily accompanied by an
important change in the physical conditions about the molecules.
Firstly, a variation of distance is attended by a change in the
relative proportions of the intercepted vibrating ether column,
whose length is determined by the intervening distance, and upon
the physical state of which the conditions of equilibrium of the
molecules intimately depend. Secondly, a variation of distance is
attended by a change in the energy of the stationary vibration of
the intercepted ether column. When the molecules are placed
in very close proximity, the intercepted ether column becomes
short relatively to its breadth, the lateral area afforded for expansion
becomes contracted, and the pulsations of the column are more
concentrated against the opposing molecules, tending to separate
them ; also the energy of the stationary vibration of the column has
been increased, owing to the increased proximity of the molecules.
It would appear reasonable to conclude from this that the physical
influence producing a " repulsion " would predominate in the nearest
proximity to a molecule — an inference which accords with observed
facts.

On the other hand, when the separating distance of two mole-
cules is increased, the intercepted ether column becomes long
relatively to its breadth, more lateral area is afforded for expan-
sion, which would conduce to a rarefaction of the column, a result
favourable to an " attraction." Also, the energy of the direct
action of the pulsations of the column has been reduced by the
increase of distance. To take an illustrative case : The aggrega-
tion of vibrating molecules, known as the '* solid," comport them-
selves in such a way that when the distance of the molecules is
reduced, they "repel," and when the distance is increased the
molecules '* attract," or a solid resists an attempt both to compress
and to dilate it, each molecule taking up a position or point of
stable equilibrium, the situation of which point varies by a change
of vibrating energy (change of "temperature "). In order for the
general phenomena of alternating *' attraction " and " repulsion "
exhibited in the case of molecules to be produced, it is only
necessary that the two opposing physical influences which deter-
mine the equilibrium of the molecules should not preserve the
same constant ratio to each other under the varying physical
conditions attendant on a change of distance. Thus the diminution
of the ascendant influence up to equality and beyond, by an
increase of distance, would produce alternating attraction and
repulsion, separated by a neutral point of equilibrium.

70. We will now notice a few of the facts as they actually
exist. Although there are some exceptions in the case where the

46

vibrating periods of the molecules differ, there is a broad or
general agreement in certain of the effects observable, more
particularly in the case where the vibrating periods of the mole-
cules are the same. The aggregation of molecules in the solid
state in the vast variety of materials forms an instance where the
vibrating period of the aggregated molecules is the same. Now,
in the general case of molecules of similar vibrating periods, and
also in certain other instances, the first marked effect observable
on approaching the molecules towards each other, is a repulsion ;
then by a further approach there is an attraction, and in the closest
proximity there is again a repulsion. Thus, in the general case of
solid bodies, two separate portions of the same substance will not
readily unite even when pressed together, or the molecules in the
first instance repel. It is practicable in certain cases to apply a
suiBcient pressure to overcome this first repulsion, and to bring
the molecules into proper proximity for the attraction to come
into play. Thus, two freshly cut surfaces of lead may be made to
unite by pressure, this being also the case with glass and some
other substances. After this degree of approach has been attained,
i. e. after the molecules have taken up those positions of stable
equilibrium which constitute the aggregation of the molecules in
the solid state, then a pressure is necessary in order to cause a
further approach, and the molecules recoil or recede into their
previous positions of stable equilibrium when this pressure is
removed ; so that therefore the attraction changes into a repulsion
in the nearest proximity to the molecules.

71. Since, therefore, the repulsion experienced on the first
approach of two molecules changes into an attraction by a further
approach of the molecules, it follows that a certain point must
exist at a certain definite distance outside a molecule (the vibra-
ting energy being supposed kept constant), at which point, if a
second similar molecule be placed, it is in equilibrium ; but if the
molecule be placed a short distance outside this point, it is repelled ;
and if it be placed a short distance inside this point, it is attracted.
Accordingly, since the shifting of the molecule to a short distance
to either side of this point causes it to be driven farther away
from the point, this point might, therefore, be termed ** the neutral
point of unstable equilibrium," where repulsion changes into
attraction.

Further, since after this neutral point has been passed and
the attraction coming into play, the molecules are urged a short
distance towards each other, each molecule then takes up a
position of stable equilibrium, where attraction changes (inversely)
into repulsion ; it follows that a second neutral point must exist
outside a molecule (in nearer proximity to the molecule than the
first neutral point), at which point, if a second similar molecule be
placed, it is in stable equilibrium. Since also when the molecule
is shifted to a short distance to either side of this second neutral

47

point, it returns to it again when left to itself, or when the dis-
turbance ceases ; this second neutral point in nearest proximity to
the molecule might, therefore, be termed " the neutral point of
stable equilibrium."

72. As an illustration of this deportment of molecules when,
' instead of separate portions of a solid, separate or discrete mole-
cules are concerned, we may take the case of a vapour or gas.
As a generally applicable example, we may take the case of iodine.
This substance exists as a- vapour at the same temperature at
which it exists as a solid, as is in general the case with solids more
or less. The discrete molecules of iodine, therefore, which compose
the vapour, although at a temperature (vibrating energy) suited to
the formation of the solid state, yet these molecules can rebound
from each other in the free translatory motion of the gaseous state
without uniting. The discrete or separate molecules, therefore, as
was to be expected, deport themselves towards each other as two
separate portions (i. e. parts composed of a number of molecules)
of the solid substance, or the discrete molecules forming a vapour
or gas comport themselves towards each other, as the outer layer
of the molecules of a portion of the solid substance would comport
themselves to the outer layer of the molecules of another separate
portion of the same substance, i.e. the molecules in the first
instance repel.

As an example of a similar fact in a case where the vibrating
periods differ, we might instance the case of oxygen and hydrogen
gases, a mixture of which in a proportion suited to an explosion
may be kept for any length of time without the molecules uniting;
and although the molecules are interchanging motion among them-
selves in free translatory motion, they do not under normal con-
ditions come into sufficient proximity to unite. In order to effect
this, some disturbing cause is necessary, such as, for example, the
application of incandescent matter (matter in intense molecular
vibration), or perhaps a sudden forcible concussion.

73. The Beeiprocity of Attraction and Bepuhion, — It is a note-
worthy fact that a complete reciprocity exists in the phenomena
of attraction and repulsion, or, in other words, each of the two
masses or molecules concerned is acted on with precisely equal
energy. This has been experimentally proved, in the series of
experiments before noticed, to be a characteristic of the effects
produced by vibrating masses generally.

In one case specially described, a vibrating tuning-fork wa»
suspended in such a way as to be free to move, and on a piece of
card being held near the fork, the latter moved towards the card,
precisely as (conversely) the freely suspended card would have
moved towards the fixed vibrating fork. The description adds :
'* Hence, to whatever cause the approach is due, the action is
mutual."

Now, it may be shown that this mutual action is one of the

48

necessary consequences of the fact of the existence of stationary
vibrations in the medium between the influencing masses, as in
this special case, in the column of air intercepted between the
vibrating prong and card; the same considerations applying
to vibrating molecules as to any vibrating masses whatever.

The physical characteristic of a stationary vibration being a
mutual or reciprocal reflection of the pulsations of the intervening
column of the medium from the surfaces of the opposed masses,
reciprocity of action is therefore a necessity, the energy of the
movement of either mass depending solely on the relation t^hat
the pressure of the intervening column of the medium in stationary
vibration bears to the normal pressure of the medium ; as in the
present case, the energy of the movement (approach) of either
the fork or the card depends on the relation that the pressure
of the intercepted rarefied column of air bears to the normal air
pressure, and this pressure of the vibrating air column intercepted
between the prong and card must be mutual or equal for each
surface, since the pulsations of the column are mutually reflected.
The intercepted vibrating air column abuts against the opposing
surfaces of the prong and card, the pressure being propagated
between the surfaces by mutual reflection, so that a perfectly
mutual or reciprocal action becomes a necessity ; indeed, the one
pressure owes its existence to the opposite reacting pressure.

In the same way in the case of molecules, reciprocity of action
is the necessary consequence of the mutual reflection of the
emitted waves ; the common movement of two vibrating molecules
towards or from each other (attraction or repulsion) depending
solely on the fact whether the pressure of the intercepted ether
column in stationary vibration is greater or less than the normal
ether pressure.

74. From the above considerations, therefore, the general con-
clusion follows that one of the necessary results of a stationary
vibration of the medium is to make the effects perfectly reciprocal
or mutual.

It may further be shown that the effects are not explicable by
the vibrations of the masses themselves alone, but that the
stationary vibration of the intervening medium is the sole physical
cause concerned in the phenomena of attraction and repulsion, and
the mere emission of waves without the action of the stationary
vibration of the mediv/m would be incompetent to produce the
effects.

This may be proved from the following considerations. Firstly,
the production of waves is not in itself attended on the whole by a
rarefaction or absolute displacement of the medium, tlie condensa-
tion in the one half of the wave being the equivalent of the rare-
faction in the other half, and it is only when the waves become
stationary by mutual reflection, and the energy thus accumulates
at a Dxed spot, that a peimanent rarefaction of the medium can

49

be produced. Now, since a rarefaction of the medium constitutes
the only possible physical means by which an attraction (approach)
can be produced by vibration, and, further, since a rarefaction is
only possible under the condition of a stationary vibration of
the medium, it therefore follows that a stationary vibration of the
medium can be the sole physical cause concerned in producing an
attraction.

75. When justly viewed, the observed experimental fact pre-
viously referred to, where a fixed card attracts or causes the
approach of a freely suspended vibrating tuning-fork, affords in
itself a complete illustration of the truth of this principle. In this
case the card does not vibrate at all, and yet the card acts upon
the fork with the same force that the vibrating fork acts upon the
card. This equality of action, therefore, proves at once that
the vibrations of the fork give it no special advantage, or the
waves emitted by the fork have of themselves no special influence
independent of the stationary vibration of the intervening air
column ; for if this were the case, the effect would be one-sided
and not mutual. The very fact that the mass which does not
vibrate at all can produce as great an attraction as the mass which
vibrates, itself proves that that which is concerned in the effect
must be sometning independent of the vibrations of the mass
itself, and, moreover, something placed under such physical con-
ditions as to make the effect mutual. This- is only true of the
intercepted column of the medium in stationary vibration, whose
pressure (whatever its value) must affect both opposing masses
equally, the effect being solely dependent on the stationary vibra-
tion of the intervening medium, the effect produced by a mass
being (by a given energy of vibration of the intercepted column of
the medium) independent of the fact whether the mass vibrates or
not ; or by a given energy of the stationary vibration of the inter-
cepted column of the medium, the effect is the same whether one
or both masses vibrate, or they vibrate with different degrees of
energy. This point is further illustrated by the observed perfect
reciprocity of action in the case of aggregated molecules, whose
vibrating periods and vibrating intensities differ (chemically
combined molecules). The stationary vibrations produced in the
intervening medium by the mutual reflection of the emitted waves,
therefore, constitute the sole physical cause concerned in the
effects comprised imder the phenomena of " attraction and repul-
sion," and the action of the stationary vibrations is also the sole
means by which the reciprocity of the effects admits of being
explained.

76. The only conceivable way in which a vibrating suspended
tuning-fork could be affected by the presence of a distant card, is
that the medium about the fork is in some way affected by the
presence of the card. Now, since the card does not itself vibrate,
the only possible way that it can affect the medium about th^

50

fork is by reflecting the impinging waves back upon the fork, by
which stationary vibrations are produced in the intervening
medium, and to these stationary vibrations alone, therefore, can
the approach of the fork possibly be referred. Further, since
in the converse case when the fork is fixed and the card movable,
the card is acted on with precisely equal force, it follows, there-
fore, that the same physical cause, i. e. the stationary vibrations of
the medium, must be solely concerned in this case also, i. e. in
both cases, whether it be the approach of the vibrating fork or the
approach of the card.

It may be further observed in the illustrative case of the
vibrating freely suspended fork and fixed card, that unless the
reflection by the card of the emitted waves, back upon the fork
(and the consequent production of stationary vibrations in the
intervening medium), be taken into account, by which means
the medium about the fork at that special side of the fork where
the card is situated is specially affected, it would be a complete
impossibility to explain why the presence of a card should cause a
vibrating suspended fork to commence moving towards it; for
unless these stationary vibrations were produced, the medium
about the fork would be in precisely the same physical state when
the card is present as when the card is absent, and consequently
there would be no more reason for the suspended fork to com-
mence moving in a particular direction (to be " attracted ") when
the card is present than there would be when the card is absent,
the same reasoning applying in the case of molecules as in the
case of any masses of matter whatever.

77. The above considerations all lead to the general conclusion
that the stationary vibrations produced in the intervening medium
are the sole physical cause concerned in the phenomena of attraction
and repulsion, and that the mere emission of waves, independent
of the stationary vibrations, would be incompetent to produce the
effects.

78. There is one point, perhaps, worthy of notice in regard to
the establishment of reciprocity of action, viz. that this must
require a certain time to establish itself, excepting in that special
case when both masses commence to vibrate at the same instant
and with the same energy. Thus, if we suppose the case where
one mass is put in vibration after another mass has been placed in
the vicinity, then in such a case the inference is necessary that
the action would be without reciprocity for a short period, or one
mass would be acted on alone for a short period. Thus, if we take
the illustrative example of a tuning-fork and card, and suppose
that the card is first brought into the vicinity of the fork, and
then that the fork is put into vibration ; then it is necessary to
conclude that the card would be influenced a certain fraction of
time before the fork; for the vibrations of the medium become

stationary at the card at the instant when the wave reflected

51

from the card meets the emitted wave, i. e. at the instant when
the reflected wave commences its return, whereas the vibra-
tions of the medium cannot become stationary at the fork imtil
the reflected wave has completed its return, i. e. has traversed the
entire interval between the card and fork, and has reached the
fork. Until the vibrations of the medium become stationary at
the fork, or until the emitted wave reflected from the card has
reached the fork, the fork cannot possibly be influenced by the
presence of the card, for before the reflected wave reaches the
fork the medium about the fork continues to remain in precisely
the same physical state as if the card were not present. Hence, in
such a case, the inference is necessary that the one mass is affected
before the other, although after the completion of the stationary
vibration of the medium reciprocity becomes perfect, the time
required for reciprocity to establish itself being represented by the
time required for the wave to traverse the intervening distance
separating the masses. These considerations possibly might have
a more important application in a case where the separating
distance of the influencing masses was great.

SECTION VL

79. Mode of the Development and Absorption of Heat in Expansion
and Contraction. — It is a known fact that by the compression or
contraction of matter heat is generated, and by the expansion of
matter heat is absorbed ; but the mode or physical process by
which this result is attained, or the cause why a mere movement
of translation of the molecules of a substance in a particular
direction should cause the molecules to vibrate with increased
energy, and a movement of translation in the opposite direction
should cause the molecules to vibrate with reduced energy,
requires explanation.

This may be shown to be another of the necessary conse-
quences resulting from the fact of the existence of stationary
vibrations in the medium between opposed vibrating masses and
molecules. The character of a stationary vibration consisting
simply in an oscillation of the intervening column of the medium,
either as a whole or in parts, the extremities of the column
abutting against and rebounding from the two opposed vibrating
masses or molecules ; it follows, therefore, that an approach
of the two masses or molecules in which act each is driven
against the oscillating column, must cause the column to rebound
with greater energy, just as an elastic sphere will rebound
with greater energy when the surface from. yfTaiftt^ \^, t^wssss^

'52

is driven against it. Hence it follows, necessarily from this,
that .the act of approach of the opposed masses, such as the
approach of two vibrating molecules, will be necessarily attended
by an increase in the energy of the stationary vibration (oscillation)
01 the intervening ether column. It is, however, important to
observe that the period of vibration (oscillation) of the column
coincides precisely with the period of vibration of the molecules,
since the column is itself put in vibration by the molecules.
Hence the increase in the energy of vibration of the ether colunm,
due to the movement of approach of the molecules, must be neces-
sarily attended by an increase in the energy of vibration of the
molecules themselves, which vibrate in synchronism with the
column, and against which the oscillating column abuts, just as,
conversely, any artificial increase of the vibrating energy of the
molecules would affect the column. Thus it follows that a move-
ment of translation of two molecules towards each other, as takes
place by the compression of matter, will necessarily be attended
by an incf ease in the vibrating energy of the molecules (develop*
ment of heat); precisely analogous but converse considerations
applying in the case of the recession of the molecules (expansion).

80. The interchange of motion between two gaseous molecules
in the normal state of a gas would afford an illustration of both
processes, the vibrating energy of the molecules being increased
at their approach, and reduced at their recession ; or the two
molecules in their interchange of motion are alternately heated
and chilled. If we regard the state of the case at the point when
the rebound of the two vibrating molecules commences, then the
intercepted pulsating ether column which does the work of urging
the molecules apart, loses an amount of energy equivalent to the
work done ; or, in other words, the pulsations of the column are
reduced by an amount represented by the translatory motion
imparted to the molecules. This loss of vibrating energy by the
column necessarily reacts upon the molecules, i. e. the vibrating
energy of the column is, in the readjustment of the equilibrium
of motion, partly made good at the expense of the vibrating energy
of the molecules, the receding molecules thereby losing a certain
portion of their vibrating energy, or the molecules are chilled.

The loss of vibratory motion ('* absorption of heat ") which
accompanies expansion is beautifully illustrated by the known
experiment by which carbonic acid is produced in the solid form
by the free evaporation of the acid in the liquid form. In this
case, when the vapour is allowed to escape freely, the vibrating
molecules are driven apart with such velocity that the energy of
vibration of the ether column intercepted between any pair of
n receding molecules is so reduced by the work it performs, and con-
sequently the vibrating energy of the molecules themselves is
reduced to such a degree that the molecules become fitted to
take up the solid state.

53

81. The converse case of the augmentation of vibrating energy
(" development of heat *') in the approach of molecules (con-
traction) is well illustrated by the simple apparatus known as the
" fire syringe," by which a piece of tinder is ignited by the sudden .
compression of the air by a forcible blow struck upon a piston.
In this case the velocity with which the air molecules are driven
together is such as to augment their vibrating energy almost up
to that of flame.

82. It may be observed, that however great the energy with
which the molecules are urged together, and consequently how-
ever forcibly the intercepted ether column may be acted upon, this
need not necessarily disturb the synchronism of the oscillation of
the column, for the column can adapt itself to a more energetic
movement by oscillating through a greater amplitude, without
necessarily changing its oscillating period, and therefore without
detracting from the power which its synchronism gives it of
reacting upon the molecules.

54

SECTION VII.

83. The Dynamic Effects of the Ether. — We will now turn to the
consideration of the dynamic effects of the e'ther, and we may take
the well-known case of the formation of water, by the combination
of the mixed gases oxygen and hydrogen^ as this case serves as a
type of chemical processes, and, indeed, serves as an illustration of
tne process involved at the interchange of motion between the
ether and the molecules of matter generally ; the variety in the
effects consisting in differences in the energy of action in the case
of molecules of different vibrating periods, the variety in the
effects depending also on the greater or less number of molecules
which are in the act of combination at the same time. Thus the
glow rusting of an iron wire, and the burning of a similar wire in
oxygen gas with the scintillation of sparks, serve to represent two
cases where the differences merely depend on the differences in
the number of molecules which are in the act of combination at
the same time, each separate molecule in the rusting of the wire
entering into combination with the same velocity or intensity as
each separate molecule of the wire when burnt, only in the former
case the number of molecules in the act of combination at once
is not sufficient to disturb the ether enough for the waves to be
capable of affecting the eye.

84. If we regard a mixture of the gases oxygen and hydrogen,
then before the match is applied the vibrating molecules are in
free translatory motion, exchanging motion among themselves;

any pair of molecules at their approach throwing the ether into
"^^^^^^iBle stationary vibration, and not coming into sufficient

55

proximity to unite. In order for the molecules to combine, they
must, by the action of some force, be driven together beyond the
outer neutral point of unstable equilibrium, which, as before set
forth, separates the combined from the gaseous state. Although
the force required to effect this is small compared with the energy
M'ith which the molecules are urged together after the neutral
point is passed, it is neyertheless suflScient to prevent the spon-
taneous combination of the molecules. When, however, any
means whatever, capable of forcibly disturbing the molecules, is
resorted to, such as the application of a substance in intense mole-
cular vibration, as, for example, an incandescent solid, a flame, &c.,
or even perhaps a sudden forcible concussion, indeed anything
which suffices to drive a few of the molecules into proper proximity;
when this is effected, the rarefaction produced in the intervening
ether column thrown into forcible oscillation by any two approxi-
mated molecules, comes into effect, and the normal ether pressure
on the remote halves of the pair of molecules being thereby
brought into action, the molecules are driven forcibly together, they
approach the internal neutral point of stable equilibrium, and are
carried beyond it by their momentum, but rebound again, the mole-
cules oscillating about this point as a position of stable equilibrium.

Each pair of molecules during combination being driven at
a high speed against the oscillating ether column intercepted
between the approaching molecules, the oscillations of the column
are thereby greatly intensified, and, therefore, those of the mole-
cules which vibrate in synchronism with column, this giving rise
to the ether waves of heat and light observed at the combina-
tion of the gases. At the same time the high intensification of
the vibrating energy after combination has, by the stationary
vibrations suddenly set up in the intervening ether, the effect of
driving apart in all directions the molecules of water vapour, a
general translatory motion (the motion characteristic of gaseous
matter) being thus set up, 'the whole vaporous mass tending
forcibly to expand in all directions, and producing the effect
known as the " explosion." It is of course clear that the combina-
tion of a few molecules, in the first instance, by the application of a
flame, has the effect, by the molecular disturbance thus set up, of
causing the practically instantaneous combination of the entire
gaseous mass.

During the process of combination, the ether particles by
whose action the molecules are driven towards each other, lose
thereby a certain portion of their normal velocity ; the amount of
motion lost by the ether during the process being precisely that
transferred to the molecules. This loss of motion sustained by
the ether next the molecules commences to be replenished from
the very commencement of the movement of the molecules, the
ether particles simply continuing to exchange velocities (their
normal mode of motion), and thus the spherical wave representing

56

the loss of motion is automatically carried oflf at the velocity of
the particles themselves, or with the speed of a wave of light, so
that the ether particles next the molecules are prepared for a fresh
effort even before the gaseous molecules have had time fully to
approach each other. If it were not for this high normal velocity
of the ether particles, a sustained effort of a high intensity would
be impossible to the ether, for only on this condition could fresh
motion be drawn with adequate speed from the stores of motion
contained in the ether at a distance. Moreover, only on this
condition could the loss of motion sustained by the ether be,
during the short time of the explosion, subdivided or distributed
over a vast radial volume of the ether, whereby the local disturbance
of the equilibrium of the ether is reduced to a minimum. The
spherical wave representing tlie loss of motion sustained is carried off
with extreme rapidity, and soon, from the vast number of ether par-
ticles encountered which increases as the square of the distance, the
loss of motion becomes so subdivided that, although existing as a
whole, it soon practically ceases to exist as regards each particle
taken separately.

85. From the known mechanical value of the process of com-
bination of the gases oxygen and hydrogen, it may be computed
that if the entire energy given up by Sie ether were expended
solely in developing the translatory motion of approach of the
molecules in the process of combination, the maximum velocity
imparted to the hydrogen molecule would amount to about nine
miles per second ; but since it is necessary to conclude that the
translatory motion of approach of the molecule from the instant of
its generation commences to be converted into vibratory motion
(heat), it would follow that the full value of the translatory motion
cannot be attained, although the inference appears warranted that
a considerable part of the full value is attained ; for, firstly, since
the intensity of the vibratory motion (heat) depends on the
velocity with which the molecule is urged against the oscillating
ether colunm, the observed intensity of the heat therefore indicates
that a high velocity of translation must have been attained by the
molecule ; and secondly, the inference is necessary that the most
intense development of vibratory motion (heat) takes place on the
shortening of the ether column at the approach of the molecules,
the vibrations of the column (due to the rapid forward and back*
ward reflection of the pulses attendant on its reduced length)
being then intensified most forcibly; and, therefore, by reaction the
vibrations of the molecules, the molecule then also having acquired
its greatest velocity, and having reached the inner neutral point
where the work of the ether ends, the molecule being driven
by its momentum against the oscillating ether column from
which it finally rebounds, and coming to the end of its path by
converting its translatory motion into vibratory motion (heat).
From these considerations, therefore, it would follow that the

57

greatest development of heat takes place, not during the develop-
ment of the translatory motion, but afterwards, the translatory
motion being first developed in great part, and then converted
into heat, so that from this the inference would be warranted that
the full mechanical value for the translatory motion is nearly
attained.

The combination of the mixed gases oxygen and hydrogen
being one of the most intense examples of chemical action known,
and the mass of the hydrogen molecule being exceptionally small,
it would follow that the velocity of the hydrogen molecule in this
case must constitute one of the highest instances of molecular
velocity developed in chemical action. However, even if the full
value of the velocity (nine miles per second) were attained, this
velocity constitutes but a small fraction of the normal velocity of
the tither particles (that of a wave of light), so that it becomes
apparent that the ether is an agent mechanically well adapted to
follow up and to effect with ease the rapid movements of the mole-
cules of matter even in the most intense instances of chemical
action, as in the case of explosives, rapid combustion, &c. ; or, in
other words, the ether is, from the high normal velocity of its
particles, an agent physically adapted to effect those extremely
rapid changes in the positions of equilibrium of molecules, exhibited
in the general phenomena of chemical action.

If, on the other hand, the ether particles did not possess a high
normal velocity, or if by the same amount of enclosed energy the
mass of the particles were greater and the speed less, then the
production of the same velocity of motion in the molecules of
matter could not take place without the loss of a considerable
percentage of their absolute velocity by the ether particles, which
would be attended by a palpable rarefaction or disturbance of the
equilibrium of pressure of the ether ^ for it is important to observe
that not only can a given decrement of velocity be sustained by
the particles with a less disturbance, as the absolute velocity
of the particles is greater, but also the disturbance is less from a.
second cause when the absolute velocity of the particles is greater;
for the speed with which the wave representing the loss of motion
is carried off, and consequently the volume of the ether over which
the loss of motion is subdivided, depends on the absolute normal
velocity of the particles, the disturbance being less in proportion as
the number of particles over which the lois of motion is subdivided
is greater. Hence a high noimal velocity of the particles of the agent
contributes from two separate causes to reduce the disturbance of the
equilibrium of the agent attendant on the production of a given
dynamic effect. The existence of a high normal velocity for the
ether particles is therefore the essential mechanical condition to
render the ether adapted as a motive agent in an intense and long-
continued development of motion, as exhibited in the intense
molecular motion of rapid combustion, &c. On account of the

58

high absolute normal velocity of the ether particles, the propor-
tionate loss of velocity sustained by the particles even in the most
intense instances of chemical action, such as the explosion of gun-
powder, for example, is not sufficient to produce a palpable
disturbance of the equilibrium of the ether, and the loss of motion
is rendered imperceptible by rapid distribution over a vast volume
of the ether.

SECTION VIII.

86. Correlation of the Effects of Air Waves and Ether Waves, —
The mutual approach of two molecules vibrating in the ether may
be compared to the mutual approach of two (freely suspended)
tuning-forks vibrating in air, or to the approach of a freely
suspended piece of card or plate of any substance towards a tuning-
fork vibrating in air.

The motion of the card or plate towards the vibrating fork
being due to the excess of the normal air pressure at the back of
the plate, over the reduced air pressure in front, due to the rarefac-
tion produced by the stationary vibration of the air column inter-
cepted between the vibrating prong and the plate ; then when the
motion of the plate towards the fork commences, the air molecules
which rebound from the remote surface of the plate lose a portion
of their velocity by transference to the plate. This loss of velocity
is rapidly restored by the neighbouring air molecules in the inter-
change of motion continually taking place between the molecules,
and thus the loss of motion is carried off into the surrounding air
in the form of a wave, and at a speed somewhat less than the
normal speed (sixteen hundred feet per second) of the air mole-
cules, or with the speed of a wave of sound.

87. Though the effect must be extremely feeble here, it is theo-
retically deducible that the energy of vibration of the fork must,
during the approach of the plate (in analogy with the development
of vibrating energy (heat) at the approach of molecules), be slightly
augmented, due to the intervening vibrating air column being driven
against the prong with M^hich it vibrates in synchronism. The effect
here must of necessity be extremely feeble, neither the rate of ap-
proach nor the energy of vibration in this case being at all com-
parable with the case of molecules ; also the effect would be probably
more than masked by the dissipation of the vibrating energy of the
fork into the surrounding air during the approach, for the vibration
of the fork, unlike that of the molecule, is not continuously main-
tained by external sources. However, a physical cause must have
its effect whether it be feeble or not.

It 18, therefore, important to observe that the work done at the

59

approach of the plate cannot be directly due to the vibrations of
the fork, for if the movement of translation of the plate were
derived from the vibrating energy of the fork, then the approach
of the plate would have the effect of reducing the vibrating energy
of the fork by an amount equivalent to the work done, whereas
the approach of the plate has the exact contrary effect. The
motion imparted to the plate must, therefore, be entirely derived
from the surrounding air, whose molecules lose an amount of
motion or energy equivalent to the translatory motion imparted to
the plate, including the small extra amount of vibratory motion
imparted to the fork during the approach of the plate.

The vibrations of the fork have the indirect object of main-
taining the rarefaction of the air in front of the plate, or they
serve the purpose of putting the air into a suitable physical con-
dition such that an interchange of motion can take place between
the molecules of air and the plate, the air molecules alone, and
not the vibrating fork, being the source of energy in the approach
of the plate, the same considerations evidently applying m the
case of the mutual approach of two (freely suspended) vibrating
forks.

88. So in the case of the approach of two molecules vibrating
in the ether, the energy concerned in effecting the approach (com-
bination) of the molecules can be solely derived from the surround-
ing ether, and not from the vibrations of the molecules themselves.
This is illustrated by the observed effects; for if the energy
concerned in the approach of the molecules were derived or
abstracted from the molecular vibrations, then the vibrating energy
(heat) of the molecules would be necessarily reduced at their
approach by an amount equivalent to the work done, whereas the
exact contrary is the fact. The entire energy developed at the
approach of the molecules, including both the translatory motion
developed and the vibratory motion (heat) developed, must be
therefore solely derived from the surrounding ether, which loses an
amount of motion equivalent to the motion developed : the vibra-
tions of the molecules merely serving the indirect purpose of
putting the ether into a suitable physical condition, such that an
interchange of motion can effect itself between its particles and
the molecules ; the ether, and not the molecular vibrations, being
the source or motive agent of the molecular motion observed.

In the case of the combustion of a piece of coal, for example,
the molecular motion developed is solely derived from the sur-
rounding ether, and not from the molecular vibrations of the coal,
the energy of these molecular vibrations (the heat) being greatly
intensified in the process of combustion. The motion developed
in the coal and molecules of air in the process of combustion is
therefore solely derived from the motive agency of the surrounding
ether : the normal molecular vibration of the coal (sustained by
the dynamic action of the sun) merely serroi^ ^Xi*^ SsL&cfcRX»^^'Qx^<^'^^

CO

of putting the coal in a fit state, such that an interchange of
motion can effect itself between its molecules and the ether, or a
mass of coal is simply a piece of mechanism for utilizing the motion
of the ether.

89. The above considerations serve to indicate that in addition
to the well-known striking analogy which exists between the
effects of ether waves and those of air waves, as exhibited in the
phenomena of light and sound, a still further analogy exists as
regards the effects due to a disturbance of the equilibrium of
pressure of the medium by the action of the waves, as exhibited
in the movements (** attractions," &c.) of masses vibrating in air,
and of molecules vibrating in the ether; the intensity of the
effects in this latter case being greater in proportion as the
intense ether pressure renders possible effects of a higher static
value, and in proportion as the energy of the vibrations of mole-
cules sustained by the powerful agency of the sun, incomparably
surpasses the feeble vibrations mechanically produced in masses.

SECTION IX.

90. We have referred to the decrement, or loss of motion,
sustained by the ether particles in developing motion in the mole-
cules of matter (in chemical action, &c.) as a "wave." Now,
since the term ** wave" in general applies to regular or periodic
increments and decrements of velocity experienced by the com-
ponent particles of an aeriform medium, the periodic character of
such waves enabling them to accumulate motion, so as to be
capable in certain cases of affecting the senses (as in the pheno-
mena of light and sound) ; it is well, therefore, to distinguish the
true character of the wave representing the loss of motion sus-
tained by the ether in the production of any movement or
dynamic effect. Although it is necessary to conclude that in the
performance of work by the ether, as in the case of combustion,
for example, a separate wave, representing the equivalent loss of
motion sustained Tby the ether, must be produced at the approach
(combination) of each separate pair of molecules ; still this could
not be regarded as a ** wave " in the ordinary sense, since this
form of wave represents only a decrement of motion, and not an
equal increment and decrement, of which a " wave " consists in
the general meaning of the term. Moreover, these decrements of
motion sustained by the ether as the motive agent in the move-
ment of approach of the molecules, do not in any way follow in
regular or periodic succession as in the case of** waves commonly
8o termed, and by which they are enabled to affect the senses, but

61

these waves or decrements of motion are superimposed upon each
other, and the distinctive character of each wave (i. e. the wave
attendant on the approach of each separate pair of molecules) is
lost, or the waves are necessarily merged into each other, which
would tend to produce simply an appreciably uniform loss of
motion in the ether around, spread over a vast concentric volume
of the ether, the loss of motion being proportionally very small as
regards each ether particle taken separately, the loss diminishing
uniformly as the square of the distance from the origin. If we
regard an isolated wave, or the decrement of motion developed in
the ether at the combination of a single pair of molecules, then
this wave being due to the translatory movement of approach of
the entire mass of the molecule, would be of disproportionately
greater length than the rapid and periodic waves of heat simul-
taneously generated due to the vibrations of the molecule during
its approach, these short waves of heat being, therefore, super-
imposed upon the wave representing the decrement of motion :
the short waves (waves of heat and light) being also capable, from
their periodic character, of appealing to the senses.

So in a somewhat analogous manner the wave or decrement of
motion developed in the air, at the mutual approach of two vibra-
ting suspended tuning-forks, and which represents the loss of motion
sustained by the molecules of air in urging the forks together,
must be of much greater length than the periodic waves due to
the rapid vibrations of the forks during their approach, these
short waves being superimposed upon the wave representing the
decrement of motion. The disproportionately greater length of
the wave representing the decrement of motion will become
apparent when it is considered that if the approach of the forks
lasted but one second, the loss of motion would in that time be
spread over a spherical mass of air of more than a thousand feet
radius, or the loss of motion is so subdivided as to be totally
incapable of appealing to the senses in any way, while, on the
other hand, the periodic character of the waves due to the vibra-
tions of the forks (the waves of sound) enables these waves to aflfect
the senses.

SECTION X.

91. The Static Effects of the Ether.— We will return here to
the consideration of the static effects of the ether as exhibited in
the phenomena of " cohesion," chemical union, &c., i. e. the general
phenomena of the aggregation of molecules.

As an illustrative example having a general application, we
may take the case of a metallic bar submitted to o. ti&\i%\k.^ ^^^^s^.

62

Though in reality it is impossible to apply a tensile strain to
matter, since matter consists of discrete or wholly unconnected
parts (molecules and particles) separated by empty space, and it
is impossible to direct a strain across empty space, or to put space
imder strain, still the term " tensile strain, ' in contradistinction to
" compressive strain,'* may be convenient in practice to denote
the particular direction in which it is desired to produce motion.

92. If 6, c, d, &c., Fig. 6 (i.), represent any line of molecules
in the direction of the length of a metallic bar, these molecules
being in equilibrium with the ether pressure, and at a certain
distance apart, which remains constant so long as the vibrating
energy (** temperature ") of the bar is kept constant. Then when
the bar is said to be under a "tensile strain,'* the direction of the
movement of the molecules is from each other, or the ends of the
bar are moved to a greater distance apart. We will consider,
therefore, any single molecule 6, and suppose it to be moved to a
greater distance from the next molecule c, taking up the new

position y (ii.), it being supposed that the

^^^' ^- farther end of the bar is fixed. Then the

( I) ? J J J J equilibrium of the ether pressure is disturbed

by this movement of the vibrating molecule

(ll)**5* •. ^^*^ ^ ^®^ position, the energy of the sta-

f tdc h tionary vibration of the ether column inter-

(III) }

• • • • cepted between h and e being reduced by
e^d o' P the increase of the distance of the two mole-

cules, the eflfect being that the pressure
(IV) ^. •. J. •. |. exerted by the vibrating column upon the

opposing halves of the molecules h' and e
is reduced, the pressure of the column being necessarily reciprocal,
or equal for each molecule, owing to the mutual reflection of the
pulsations. The ether pressure upon the opposite sides of the
molecule c is therefore no longer equal, the lengths of the two
oscillating ether columns at opposite sides of the molecule being
unequal, the molecule is therefore driven into a new position o'
(iii.)^ or the molecule is moved by the ether pressure, until by
its increased distance from the next molecule d, the ether pres-
sure upon the opposite sides of the molecule c' becomes again
equal, the same considerations applying to all the molecules of
the bar. The effect of moving the end molecules of the bar
outwards (as in the case of a " tensile strain ") has, therefore,
the result of causing all the vibrating molecules of the bar to
recede to uniformly increased distances (rv.), this uniform dis-
tance of the vibrating molecules being the physical condition
required for uniformity in the ether pressure, by which the posi-
tions of equilibrium of the molecules are regulated. During the
time the strain lasts, therefore, the value of the ether pressure
between, the opposed vibrating molecules of the bar (i. e. where
the molecular distanceB are abnormally increased) is less than the

63

normal ether pressure existing outside the bar, by an amount
which represents the static value of the strain.

The mode of action in the case of a tensile strain, in some
respects at least, although the analogy
is evidently not strict, admits of rough Fig. 7.

illustration, if we suppose a glass tube, / , \ | i i i i i i
Fig. 7 (1), containing a series of sliding ' Invrvop

discs, Z, m, n, o, p, Stting air-tight in (2)----aiIEIIZDCIB—
the tube, the spaces between the discs o nc n; o' p'

being supposed occupied by air at or-
dinary atmospheric density, the discs being thus in equilibrium,
or the air pressure, i. e. the energy of the impacts of the air
molecules upon the opposite sides of each disc is the same. If,
then, the two extreme discs be moved outwards, as occurs in the
case of a tensile strain, the remaining discs will all take up new
positions of equilibrium ?, m, ti', o', jp' (2), such that the inter-
vening distances become again equal to each other, this being the
condition required to satisfy the equality in the air pressure upon
the opposite sides of the discs, the whole system bemg uniformly
distended, and returning to its previous position of equilibrium
when the strain ceases.

93. There would be, perhaps, a natural tendency to assume
that because the density of the ether is so extremely low, the
distance of its particles must be proportionately great, and that,
therefore, this agent would not be physically adapted to control
steadily and forcibly the molecules of matter in positions of stable
equilibrium, such as to control the molecules of a steel bar, for
example. It is, therefore, well to keep practically in view the fact
that although this agent has a very low density, yet its component

E articles may be in extremely close proximity, or the agent may
e extremely compact and well adapted to exert a perfectly
uniform pressure about a molecule, for there is no limit to the
degree of close proximity into which the particles of the medium
may be brought by the simple means of an extreme state of sub-
division of the matter forming the medium. Since this extreme
state of subdivision is undoubtedly the fact in the case of the
ether, it is well, therefore, in dealing .with the phenomena of
** cohesion " or the static effects of the ether generally, to realize
clearly and practically the ether as an extremely close and com-
pact body, although possessing an extremely low density. In
other words, although the density, i. e. the volume of matter
relatively to the volume of space, is small in the case of the ether,
still there is nothing to prevent the particles from being in ex-
tremely close proximity to each other, under the simple condition
of an extreme state of subdivision, the agent thus becoming very
close and compact, and mechanically well adapted to control
forcibly the molecules of matter in positions of stable equilibrium.

64

SECTION XI.

94. Maximum Valines of Cohesion, &c, — The phenomena of
"cohesion," ''chemical union," &c., or the general phenomena
of the aggregation of molecules being dependent on the molecular
vibrations as a physical cause, it would therefore be reasonable to
conclude that variation of vibrating energy (variation of " tempe-
rature ") would have a most marked influence on these phenomena ;
as is found to be the fact. Further, since when a physical cause
ceases to exist, the eflfect also ceases; it follows that at the
absolute zero of temperature (absence of vibrating energy) the
general phenomena of " cohesion," including the aggregation of
molecules in " chemical union," would cease to exist. Also, since
an increase of vibrating energy (elevation of" temperature") above
a certain degree has the eflfect of separating all molecules from
each other, as illustrated by the eflfect termed "evaporation" in
the case of molecules of similar vibrating periods, and the eflfect
termed " dissociation," in the case of molecules of dissimilar vibra-
ting periods (molecules aggregated in chemical union), it follows,
therefore, that a maximum value must exist for "cohesion," or
in the case of the aggregation of molecules generally ; or for
every substance a certain degree of vibrating energy (temperature)
must exist, which is most favourable to the stable aggregation
of the molecules; an elevation of temperature above this point, or
a fall of temperature below this point, being both followed by a
weakening of the cohesion of the molecules of the substance.

Since the aggregation of similar molecules to form masses
(usually distinctively termed " cohesion ") has a less stability than
the more intimate grouping of dissimilar molecules about a com-
mon centre in definite numbers (definite proportions) to form
clusters or compound molecules (chemical union), it would be
reasonable to conclude that signs of a weakening of the molecular
action, by lowering the temperature, would first present themselves
in the case of "cohesion," though it is quite possible that the
comparatively feeble means of reducing temperature at our com-
mand (when compared with the absolute temperature) might not
be suflBlcient to give marked signs of a weakening of the molecular
action. We are not aware that experiments with the best possible
means for lowering the temperature have been made with this
special object, nevertheless there may be certain eflfects which
have presented themselves, and which would tend to illustrate
this point. Thus it is a well-known and prevalent opinion,
grounded on observation, that metals, such as iron, become brittle
or more liable to fracture at low temperatures, which would indi-
cate a weakening of the molecular action ; indeed, it is perhaps
scarcely a questionable point that an extreme reduction of tem-
perature does conduce to render substances brittle or more friable,

65

which would tend to the same conclusion. However, since all
substances on the earth's surface have a high absolute temperature,
it would not perhaps be reasonable to expect marked eflFects to
present themselves under the circumstances of the case. If, on
the other hand, we turn to the case of cosmical matter in space,
which may recede to vast distances from the sun, then the conclu-
sion is necessary that the eflfect in question must occur. Although
the absolute zero of temperature cannot be said to exist anywhere,
since the stellar radiations must have their eflfect in all parts of
the ether of the visible universe, still in the case of masses removed
to vast distances from the sun, where the wave movement set up
in the ether by the sun's action might be practically said to have
ceased to exist, then the conclusion is necessary that the almost
total loss of vibrating energy by the molecules of the mass by
continual dissipation in the ether, must have its eflfect on the
energy of the molecular action dependent on vibrating energy,
resulting in almost total loss of cohesion by the mass. It is
quite possible, however, that such eflfects under these conditions
might escape our notice. However, there may be certain ob-
served facts which would point to this, and which may perhaps be
worth noticing in connection with this subject. Taking the case
of those cosmical masses known as meteors: these bodies are of
relatively small mass, and are known in some cases to recede to
vast distances from the sun, the orbits of some of them having
been determined, and, as a significant fact, identified in certain
cases with those of comets. If there were an actual physical
connection between these bodies and comets, it would appear as
if an actual change or disintegration of the matter of these bodies
were going on. The small mass of these meteoric bodies, and the
great distances to which some of them recede from the sun,
would be precisely the two physical conditions most favourable to
produce the eflfect in question. What may be the origin of the
meteoric dust known to exist ? We do not mean to put forward
that there is actually conclusive physical indication of the disinte-
gration of matter at a low temperature, but what evidence there is
would seem to favour the conclusion, which is at all events a
necessary one on theoretic grounds.

The possibility of the separation of the molecules of matter
eflfecting itself at a low temperature would appear to have an
important bearing on the question as to the perpetuity of phy-
sical phenomena, or the continuance of physical change in the
universe ; for the separation of molecules would be the one
condition necessary to render possible the eventual combination
of the molecules under the action of the ether with the evolu-
tion of heat and light, or this would be the physical condition
required for physical processes to recur or to repeat themselves,
as consistent with the continuance of physical change and activity
in the universe.

66

SECTION XII.

95. Mechanical Value of the Action of the Ether on Molecules. —
We may here cite a few facts and figures illustrative of the great
energy of tlie molecular phenomena, the contemplation of which
in connection with a definite physical cause may have some
interest ; the great energy and intense pressure of the ether being
well illustrated by these phenomena.

We will take the well-known substance, water. It is a known
fact that the energy developed at the combination of 8 lb. of
oxygen with 1 lb. of hydrogen is mechanically equivalent to
47,000,000 foot-lb. From this it may be deduced that by the
explosion of the mixed gases, the intensity of the energy deve-
loped would be adequate to project the mass of liquid thus formed
to a height of eight hundred and forty miles in opposition to
gravity.

The ether pressure which urges vibrating molecules together
being, on account of the action of the stationary vibration of the
intervening medium, necessarily perfectly reciprocal or equal for
each molecule, and the mass of the oxygen molecule being eight
times that of the double hydrogen molecule constituting the water
molecule; also since the velocity developed is inversely as the
mass, it follows therefore that in the mutual approach of the mole-
cules during the process of combination, the double hydrogen
molecule will receive from the ether eight times the velocity
imparted to the oxygen molecule. Hence it may be deduced that
the intensity of the energy imparted to the hydrogen molecule
during the process is such that it would be competent to project
the molecule to a height of about six thousand seven hundred
miles, this corresponding to a velocity of about nine miles per second
imparted to the molecule. These are simply physical facts follow-
ing from the known mechanical value of the process of combination
of the gases.

96. Now, if we knew the exact distance traversed by the
hydrogen molecule in its approach towards the oxygen molecule,
within which distance the above velocity (nine miles per second)
was acquired, it would then be possible to determine the actual
value of the portion of the ether pressure which was active in
urging the molecules together, compared with the value of gravity ;
for the distance required to be traversed under the action of
gravity in order to acquire the above velocity is known (viz. six
thousand seven hundred miles), and the static value of the phy-
sical agency which produces a given velocity in a mass of matter
is inversely as the distance traversed by the mass in acquiring

tills velocity.

67

The fact before referred to, that a certain part of the translatory
motion developed in the molecule during the short distance tra-
versed by it in the process of combiuation is converted into
vibratory motion, will not affect the comparison, the total energy
in the form of motion being the same in any case.

Although the actual distance traversed by the hydrogen mole-
cule in acquiring an energy represented by a speed of nine miles
per second is not known, still we may fix a limiting value for this
distance, or a value which is with certainty greater than or outside
the actual fact, and from this may be deduced the lov> est limiting
value for the intensity of the ether pressure which was concerned
in the effect. It may be taken as quite certain that the distance
is less than a millionth of an inch, as this distance is quite acces-
sible to an ordinary microscope, and indeed cannot be regarded as
a molecular dimension at all. It will be observed, therefore, that
by ^8 much as this distance, taken as a basis, is greater than the
actual distance, by so much will the result arrived at for the
intensity of the ether pressure concerned in the effect be less than
the reality, or be under-estimated.

In order; therefore, to compare the value of the ether pressure
active during the process of combination of the molecules with
the value of gravity, we must take the distance which would
require to be traversed by the molecule under the action of
gravity, in order to acquire the same velocity (nine miles per
second) as was acquired in the distance traversed by the molecule
in the process of combination, and we must divide the one distance
by the other. Therefore, dividing 6700 miles by Trrwoinj ii^ch, we
obtain the quotient 424 billions, in round numbers.

This result shows, therefore, that with the above limiting value
for the distance traversed by the molecule, the value of the ether
pressure which acts against the hydrogen molecule and urges it
towards the oxygen molecule is 424 billion times greater than the
weight of the double hydrogen molecule, or the value of gravity
actiug upon it. It may, as before stated, be taken as certain that
this estimate for the intensity of the ether pressure is less than
the actual fact, since the distance traversed by the molecule has
undoubtedly been taken too large. Moreover, this result only
represents the difference of the ether pressure upon the opposite
sides of the molecule, effective in the process of combination, and
not the value of the normal or total ether pressure itself. How^
ever, the result arrived at is suflBcient to indicate the high value
of the ether pressure and the high intensity of the store of motion
enclosed in the ether, as the motive agent in these forcible mole-
cular movements of matter.

97. Since the work done in separating molecules is appre-
ciably equal to the work done in the combination of the molecules,
it would be possible, therefore, from the above data, to form an
estimate of the direct tensile strain or pull that would be reqiiired^

68

•

in order to separate from each other the oxygen and hydrogen
molecules forming a given quantity of water, it being imagined
that a strain could be applied for this object. Thus, if we take a
grain of water, then the value of the strain required to separate
the molecules being four hundred and twenty-four billion times
the weight of the hydrogen molecules, and the total weight of the
hydrogen molecules in a grain of water being one ninth of a
grain ; we have accordingly 424 billions x ^ grain = 3,000,000
tons, in round numbers. This result shows, therefore, that under
the condition that a movement of the hydrogen molecule through
a distance not greater than one millionth of an inch would eflfect
separation, a direct tensile strain amounting in total value to not
less than three million tons would be required to separate the
components of the compound molecules forming one grain of
water, or this represents the absolute value of the portion (or
difference) of the ether pressure active in opposing the separation
of the molecules.

As before remarked, a millionth of an inch being unques-
tionably too large as an estimate for distance traversed, the result
arrived at for the absolute value of the strain will be by so much
less than the actual fact. Also the above result gives only the mean
value of the strain, and not its maximum value. The result may,
however, serve as a further illustration of the high intensity of tne
pressure of the ether, by which this agent is mechanically qualified
to control thus forcibly the equilibrium of the molecules of matter.
98. Importani Influence of Svhdivision, — One of the most
important practical consequences following from the extensive
state of subdivision, which is the characteristic of the molecular
condition of matter, is the vast extent of surface which is thereby
brought under the action of the ether pressure. This is a fact of
importance, by a due appreciation of which the great energy of
the action of the ether upon molecules will appear no longer dis-
cordant or inconsistent, but the fact may be brought into harmony
with ordiuarjr mechanical principles, this vast extent of surface
being the fitting mechanical condition for the production of static
and dynamic effects of extreme intensity.

If, for the purpose of illustration, we suppose a sphere one inch
in diameter to be subdivided into a number of small spheres, each
one ten millionth of an inch in diameter, then the surface thus
exposed would amount to about 5 acres, the total surface increas-
ing directly in proportion as the diameter of the spheres is reduced.
Even the air pressure upon such a surface might be reckoned by
thousands of tons. What must, therefore, be the ease with the
intense ether pressure acting upon the molecules of matter? The
extremely high figures previously arrived at as a limiting estimate
for the direct static strain that would be required to separate the
constituent gaseous molecules forming one grain of water (as
representing a portion of the ether pressure upon these molecules)

69

will no longer appear discordant when due consideration has been
given to the vast extent of surface exposed by these molecules to
the play of the ether pressure.

Some idea may perhaps be formed of this, if it be considered
that in order to bring this surface into view it would be necessary
for the quantity of water forming one grain to be spread out into
an extensive film or layer only one water molecule in thickness ;
it being realized that to separate the components of the compound
molecules the ether pressure over the entire film would have to be
acted against.

When the high intensity of the ether pressure, and the vast
extent of surface exposed to this pressure, are conjointly taken into
account, then the observed power with which molecules are con-
trolled in stable equilibrium, and the observed extreme energy of
the movements of molecules when the equilibrium of pressure
is disturbed, as exhibited in the general phenomena of chemical
action, combustion, &c., reconcile themselves with the ordinary
principles of mechanics.

SECTION xm.

99. The Impalpable Nature of the Ether. — An intimate con-
nection may be shown to exist between the normal speed of the
particles of an aeriform medium and the disturbance produced by
the passage of masses of matter through the medium.

fey the movement of translation of a mass through an aeriform
medium the resistance encountered depends (as previously treated
of in connection with the vibrations of masses and molecules) on
the amount of condensation of the medium produced in front and
of rarefication produced in the rear of the moving mass, since this
is one of the conditions upon which the amount of energy imparted
to the medium by the passage of the mass depends ; the resistance
encountered being simply the measure of the energy imparted to
the medium. If there were no condensation and no rarefaction of
the medium produced by the passage of the mass, then the
number of impinging particles which receive motion in front of the
moving mass would be equal to the number of impinging particles in
the rear, which transfer an equal amount of motion to the mass ;
but on account of the existence of the condensation and rarefaction
the number of particles which receive motion in front is greater
than the number which lose motion in the rear, the excess in the
number of particles which receive an increment of velocity for
which there is no corresponding decrement being represented by
the difference between the condensation and the i:^x.^l%s^«:s^^

70

this diflference increasing with the velocity of translation of the
mass.

Further, by the passage of a mass through an aeriform
medium, there is a second physical condition by which energy is
imparted to the medium. Although by the passage of the mass
the impinging particles of the medium in front and rear expe-
rience equal increments and decrements of velocity, the mean
value of the velocity therefore remaining unchanged ; yet this, as
previously referred to, is necessarily attended on the whole by an
increase in the sum total of the energy of the particles ; so that
this forms the second physical cause of the resistance encountered
by the passage of a mass through an aeriform medium, and this
would constitute a cause for a certain resistance, even if there were
no condensation whatever of the medium formed in front of the
moving mass.

It is of course clear that if the density of the medium were
extremely small, the resistance offered under the action of both
these causes might be extremely small.

100. It is now an important point to observe that the amount
of condensation of the medium formed in front, and the amount of
rarefaction in the rear, of the moving mass will depend on the
normal speed of the component particles of the medium, for the
speed with which the condensed wave is carried forward and dissi-
pated depends directly on the speed with which an interchange of
motion can take place between the particles, i. e. on the normal
speed of the particles.

The actual rate of transmission of the wave, though dependent
on and proportional to the normal speed of the particles, will
necessarily be to a certain extent slower than the normal speed of
the particles, from the fact of the interchange of motion between
the particles taking place also obliquely to the line transmission
of the wave. In the ease of the air, for example, the speed of
whose component molecules may be taken at 1600 feet per second,
the condensed wave of displacement due to the passage of a mass
would be carried forward at a somewhat less speed than this, or at
the velocity of a wave of sound. In the case of the air, therefore,
on account of the very moderate speed of its molecules, the re-
sistance encountered and disturbance produced by the passage of
masses, even at moderate speed, are considerable. The speed of a
cannon shot is even as great, and perhaps sometimes even greater,
than the velocity of forward transmission of the condensed air
wave in front of the shot, hence the great resistance offered by the
air to projectiles, the air molecules in the rear having barely
sufficient velocity to follow up the projectile. It is evident, there-
fore, that even if the air had as low a density as the ether, it
would, on account of the slow normal speed of its molecules, be
completely unfitted to afford passage to masses at planetary rates,
or its equilibrium would be totally upset.

71

In the case of the ether, on the other hand, the wave of
displacement is carried forward at the speed of a wave of light, so
that speeds of hundreds of miles per second are actually attained
by cosmical masses, without disturbing the equilibrium of the
ether, the wave being carried forward and dissipated so rapidly
that there is no time for an appreciable condensation to accu-
mulate in front of the moving mass. The motion of the ether
particles is so rapid that equilibrium is almost immediately re-
adjusted on the slightest disturbance, and there is not time for any
disturbing effect to accumulate. The high normal speed of the
particles of the ether is therefore one of the essential physical
conditions to adapt tfiis agent to afford free passage to cosmical
masses (the planets, &c.) at high speeds, without disturbance of its
equilibrium.

101. Hence the general conclusion may be drawn that the higher
the normal speed of the particles of an aeriform medium, the less
is the equilibrium of the medium disturbed by the passage of
masses through it, or the more impalpable does the medium
become. The higher, therefore, the normal speed of the particles
of an aeriform medium, the more does the presence of the medium
elude detection, or the more impalpable the medium becomes, and
the less probability is there for its existence to be detected by
endeavouring, as it were, to probe it with masses, i. e. to disturb its
equilibrium by moving masses of matter through it. This
deduction has its direct application in the case of the ether, the
known impalpable nature of which is another physical indication
of the high normal speed of the particles of tnis agent.

102. The Physical Qualities essential to a powerful Dynamic
Agent, — It might be considered at the first thoutrht, that because
the ether is so impalpable and its density is so low it would not
be an agent suited to produce forcible mechanical effects, or it
might be inferred, on the first consideration of the subject, that the
thin impalpable ether would not be suited to act forcibly upon the
masses and molecules of matter and produce powerful dynamic
effects, such as those exhibited in the case of explosives, &c.
Now this, like many other first impressions, will become totally
altered after a due consideration of the subject.

There is, unquestionably, a natural tendency to associate ideas
of energy with large visible masses of matter in motion. This is
not to be wondered at, since these forms of energy appeal directly
to the senses, whereas the movements of molecules or particles of
matter do not. If, therefore, misleading inferences are to be
avoided, it is well that this natural tendency should be guarded
against; for the motions of molecules and particles of matter
might well possess an intensity of energy far surpassing that of
any motions of visible masses; indeed, energy in this form might
almost attain any value however high, and yet would necessarily
be wholly incapable of appealing directly to the senses.

72

There is a certain tendency, for example, to ignore, or at least not
adequately to realize, the high intensity of the concealed molecular
motion which is termed *' heat." Thus, for instance, the energy
of a passing shot is fully realized, and yet it may be shown that
the energy of the molecular motion (**heat ") possessed by the shot
at normal temperature, and while at rest, represents about double
the energy of the translatory motion of the shot at the instant
of discharge.

The normal rate of motion (1600 feet per second) of the
molecules of air is almost explosive in its energy ; yet from the
fact that these moving molecules are too small to affect the senses
directly, there is a natural tendency to overlook the existence of
this energy. The space occupied by the air molecules being very
small compared with the space unoccupied ; if therefore we were
to imagine the component molecules of a cubic foot of air
suddenly to lose their motion, a practical vacuum would be formed,
and the sudden restoration of equilibrium would produce a
dynamic effect resembling an explosion. The stoppage of the
motion of the component particles of a cubic foot of ether would
be followed by a dynamic effect, the high intensity of which could
only be realized by an adequate appreciation of the energy enclosed
by this agent.

103. In turning to the consideration of the physical qualities
essential to a powerful dynamic agent, we may first observe that
the existence of a high velocity in the particles of the agent
in their normal state is an indispensable condition, for unless this
be the fact, an intense development of motion or an intense
dynamic effect could not be produced by the agent ; in fact, unless
the particles of the agent had a high velocity, they would be
incapable even of following up the motions of the masses in which
they develop motion. Again, this high normal velocity of the
particles is the sole condition on which the motion expended by
the agent in the production of a forcible dynamic effect can be
replenished with speed, and the loss of motion be subdivided or
spread over an extensive volume of the agent, or over a large
number of the particles of the agent in a short space of time.

Secondly, minuteness in the moving particles being the
necessary condition to render a high speed practicable to the
particles, it follows, therefore, that minuteness in the particles, or
an extremely subdivided state of the matter forming tne agent, is
a second essential condition to a powerful dynamic agent.

It is important to note that this condition is necessarily fol-
lowed by an absolute concealment of the existence of the motion
from the senses, so that for an intense store of motion or energy
to exist, the concealment of its existence is a necessary condition.

Thirdly, a low density in the agent or the existence of but a
small quantity of matter in the unit volume of space may be shown
to he an essential condition to a powerful dynamic agent.

73

This will be clear when it is considered that if space were
encumbered with a quantity of matter, i. e. if the agent were
dense, the agent would itself obstruct the very motions it develops,
or, in other words, a high velocity could not be imparted without
the motion of the moving masses being greatly interfered with
and obstructed by the agent ; so that, in fact, for the attainment of
energy, the agent must rely upon speed rather than upon mass ;
it being also a notewortliy fact that the energy rises as the square
of the speed.

Moreover, it is an important mechanical point to observe that
by the absence of mass the energy becomes more concentrated, or
by a reliance upon speed rather than upon mass, a greater quantity
of energy admits of being concentrated upon a given spot;
whereas the attainment of the same absolute amount of energy
by means of large masses and slow speeds would render it
impossible for the energy to be concentrated upon a small area
(such as against a molecule of matter, for example), which
concentration of energy is absolutely essential for the production
of intense dynamic effects.

104. The above considerations, therefore, lead to the general
deduction that to constitute a powerful dynamic agent the
essential physical conditions are, firstly, a high normal speed for
the component particles of the agent ; secondly, that the particles
should be minute, or that the matter forming the agent snould be
in an extremely subdivided state ; and thirdly, that the quantity
of matter relatively to the unit volume of space should be small, or
that the agent should possess a low density.

This deduction has its direct practical application in the case
of the ether, where we find precisely these physical qualities
developed to an extreme degree.

105. That the use of minute masses endued with a high
velocity is the proper mechanical proceeding when an intense
dynamic effect is required, is illustrated in practice in many
ways. Thus, when for any engineering purpose a powerful
mechanical effect is required, then recourse is had to gunpowder.
The effect observed at the explosion of gunpowder is simply
produced by the action of small masses of matter ("molecules')
endued with a high speed. If, therefore, gunpowder, by means
of the motion transferred to its molecules by the ether, represent
in the act of explosion the true ideal of a powerful dynamic agent,
how much more must this be the case with the ether itself ?

106. Since, therefore, we observe that a high velocity of the
component particles and a low density are the qualities essential
to a powerful dynamic agent, and since this high velocity of the
component particles is precisely the quality which necessarily
renders the agent impalpable, it follows, therefore, that the
known impalpable nature and low density of the ether, instead
of indicating that this agent is unfitted to produce ^owetC\xI

74

dynamic effects, should, when justly viewed, lead directly to the
opposite conclusion.

107. To illustrate somewhat further the connection which
exists between the speed of the component particles of an aeriform
medium and its impalpability, we may imauine the ease of a con-
lined mass of air cooled down to such a degree that the translatory
motion of the air molecules has almost ceased. Then, in such a
case, the air would become quite palpable, or by a mere motion of
a mass of matter through it, the air might be completely dis-
placed, vacua formed in parts, and the density increased in other
parts ; indeed, the molecules of air, if almost without translatory
motion, might be collected in groups. The air would, in fact, by
the almost complete loss of the normal speed of its molecules,
have lost its elasticity and the power of eluding the grasp, which
the translatory motion of its molecules at normal temperature
enables it to do.

It is important, therefore, to observe that the more palpable
the mass of air becomes, the less is the store of energy enclosed,
or the less would the air be qualified to produce a dynamic effect;
and to apply, therefore, this principle generally, the fact of a
medium being palpable would indicate that it was totally unfitted
as a dynamic agent, and conversely the fact of a medium being
impalpable, by which the existence of the medium eludes direct
detection by the senses, would, by pointing clearly to the high
normal speed of the particles of the medium, directly indicate
that the medium was well qualified as a dynamic agent.

108. If we imagine conversely the confined mass of air to be
heated, so as to increase the translatory motion of its molecules,
then the air would become more and more impalpable, it would
elude the grasp, and it would be more difficult to disturb its equili-
brium by moving masses of matter through it, and therefore the
presence of the air would be more difficult to detect by this means.
At the same time it is well to note that the more impalpable the
mass of air becomes (due to the increase of speed of its molecules),
the more intense is the store of energy enclosed, and the greater is
the pressure exerted, and the more fitted does the air become as a
dynamic agent.

These considerations have their direct application in the
case of the ether, the remarkable impalpability of which could
not be better illustrated than by the fact that no ordinary rate of
motion of masses of matter has been found capable of affecting
the transmission of the waves of light by the particles of the
ether ; in fact, the density of this agent cannot be changed by
ordinary means, the readjustment of equilibrium being so rapid,
and the agent completely eludes the grasp, or its existence escapes
the direct detection of the senses.

109. It is, therefore, a remarkable and noteworthy fact that
the very qualities which serve to conceal the existence of the

75

energy and the existence of the pressure, and, indeed, the exist-
ence of the agent itself from the direct perception of the senses,
are precisely the qualities which are absolutely essential to the
existence oi this energy and pressure, or the existence of an
intense magaziae of motion.

It may, irufact, be observed that the existence of an intense
store of energy, and the existence of an intense pressure, are not
only consistent with the fact that the ether is impalpable, but they
are the necessary consequences of this fact; for the impalpable
quality of an aeriform medium is dependent on the rapid motion
of its component particles, and this rapid motion " caimot exist
without the existence of an intense store of energy, and also the
rapid motion cannot exist without the exertion of an intense
pressure, the pressure, moreover, rising in the high ratio of the
square of the speed.

110. The existence of an extensive state of subdivision of the
matter forming the agent being the essential condition to a high
normal speed of the component particles of the agent, this very
condition renders the concealment of the motion complete ; for by
the multiplicity of particles, the mean length of path, or the
limits within which the particles can move before being inter-
cepted by other particles, is rendered so small, and the pressure
thereby rendered so uniform and perfectly balanced, that the
existence of this energy and pressure must necessarily elude direct
detection by the senses.

The greatest length of path of an ether particle might well,
under the simple condition of subdivision of the matter forming
the ether, be contained many times within the limits of space that
a molecule of matter would occupy, so that as far as any power of
detecting the motion by the senses is concerned, the particles
might as well be at rest.

»rjk 111. Concealed Motion.-^-Smce the concealment of the exist-
ence of the physical agent from the senses is the necessary result
of the enclosure of a store of motion of a high intensity by the
agent, and since, as a fact, having a general application, the con-
cealment of motion is the necessary condition to render possible a
high intensity of motion, or the enclosure of a store of energy of
a high intensity; and, moreover, since the higher the intensity
of the energy the more probability is there that its existence
should have an important influence on physical phenomena; the
investigation of concealed motion, as a general physical problem,
should, therefore, have a special interest.

As a known and instructive example of concealed motion
which has a considerable intensity, and a most important bearing
on physical phenomena, the concealed motion termed "heat"
may be referred to.

112. As a known illustration of a physical agent enclosing a
considerable store of motion, and exerting thereby a co\v^\$ife^'?i^Jvs^

76

pressure, both of which elude the direct perception of the senses,
the atmosphere may be cited. The normal speed of the air mole-
cules producing the pressure of 15 lb. per square inch being 1600
feet per second, the energy enclosed, therefore, is such that if a
mass of air next the earth's surface were suddenly freed from con-
finement, the mass of air would explode in every direction, or its
molecules would fly apart with the speed of a bullet. The air,
therefore, constitutes an instructive example of concealed motion,
and may form, as it were, a sort of stepping-stone towards the
realization of the ether. If the motion of the air molecules and
the attendant pressure be concealed, how much more cause is there
for the complete concealment of the existence of the store of
motion and the attendant pressure in the case of the ether, the
cause for concealment being greater as the moving particles are
more minute, and by their multiplicity the motion is confined
within narrower limits, and the pressure more evenly balanced ?
In the case of the air, the moving portions of matter (molecules)
are suflSciently small, or the state of subdivision of the matter
forming the air is sufficiently extensive, to conceal the motion
completely from the senses, and to render the pressure of the air
upon masses of matter so perfectly balanced on all sides that the
pressure is also necessarily concealed. It may serve to contrast
the states of subdivision in the two cases to note the fact of the
ether being mechanically suited to exert a uniform pressure about
an air molecule (as about molecules generally), while the air can
only exert a uniform pressure about a mass (collection of mole-
cules), and would be wholly incompetent to control the equili-
brium of a molecule of matter, on account of the absence of an
adequate degree of subdivision.

113. When from any cause the motion of the air molecules
becomes abnormal, i. e. takes place in any one direction in pre-
ference to another, and the equilibrium is thus disturbed, and
masses of matter are influenced on one side, then the motion and
pressure become very palpable. Such an abnormal motion of the
air molecules occurs in the case of a strong wind or hurricane, for
example. It may, however, be computed that the energy repre-
sented by the translatory motion of the air molecules in the normal
state of the air represents an energy about 120 times greater than
the energy the air would possess if moving .with the speed of a
hurricane (taken at 100 miles an hour), and yet the energy and
pressure of the air in its normal state remain concealed on account
of the perfect state of equilibrium which exists.

114. Summary of the Physical Qualities of the Ether. — We may
here give a short summary of the special physical qualities of the
ether, as serving to show their mutual connection.

I. Low Density, — The low density of the ether, or the small

quantity of matter contained in the unit volume of space in the

case of the ether, is that quality by which the ether is adapted to

77

afford free passage to masses (such as the planets, &c.) and mole-
cules of matter, at high speeds, without impediment. Second, this
quality renders the ether mechanically well adapted as a means
for the general interchange of motion hetween masses and mole-
cules of matter at a distance from each other, it being an admitted
principle of mechanics that for the free interchange of motion, or
for the production of any distant effect, lightness in the inter-
vening mechanism is the essential point.

II. Extreme Minuteness of the Ether Particles. — This physical
quality is absolutely necessary to enable the ether to penetrate
with freedom the molecular interstices of matter. Second, this
minuteness of the component particles, or extreme state of sub-
division of the matter forming the ether, by multiplying the
number of the particles, and thereby bringing them into close
proximity, is the necessary quality to render the pressure exerted
by the ether upon the molecules of matter steady and uniform.
Third, this minuteness of the component particles, or extremely
subdivided state, is the necessary condition to render a high
normal speed for the particles practicable, without disturbing
effects.

III. Hiffh Normal Speed of Component Particles, — This physical
quality is absolutely essential to constitute a powerful dynamic
agent, for without this high speed dynamic effects of a high
intensity cannot be produced. Second, this high normal speed of
the particles is the sole condition on which the loss of motion
sustained by the ether can be replenished with that degree of
speed which is essential to render a continuous dynamic effect of a
high intensity possible to the ether. Third, this high speed of
the component particles is the sole quality by which the loss
of motion sustained by the ether in producing a given dynamic
effect can be subdivided or distributed over a large volume of the
ether, whereby a notable local disturbance of the equilibrium of
the ether is prevented. Fourth, this quality is essential for the
rapid interchange of motion between masses and molecules of
matter at a distance from each other, the rapidity of intercom-
munication or exchange of motion being strictly limited by the
normal speed of the particles of the intervening agent. Fifth,
this high speed of the component particles is necessary to render
possible the existence of a store of energy of a high value, without
the encumbrance of a large quantity of matter in space. Sixth,
the high normal velocity of the ether particles is the necessary
mechanical condition to enable an intense pressure to be exerted
by the ether upon the molecules of matter, without the movements
of these molecules and masses being obstructed by the agent
exerting the pressure. For, in the first place, by this high speed
of the component particles an intense pressure is attainable (more
especially as the pressure rises as the square of the speed) without
the necessity for the agent being dense, by which the free passage

78

of masses of matter through the agent would be obstructed. In
the second place, the high speed of the component particles
enables masses of matter to pass through the agent with the least
disturbance of its equilibrium, or with a minimum of resistance
from this cause, the agent becoming almost impalpable; the
exertion of an intense pressure by the agent being itself the
necessary condition to render the agent adapted to control forcibly
the molecules of matter in stable equilibrium, as exhibited in the
general phenomena of *' cohesion,' or the aggregation of the
molecules of matter generally.

The above may serve as a general summary of the special
physical qualities of the ether ; and it may be noted that if the
attempt were made beforehand, as a mechanical problem or
speculation, to devise or scheme out what special physical qualities
an agent should possess in order to be mechanically fitted to
produce the varied physical effects of the character observed, then
the scheme of the ether would be found to constitute the only
possible solution of which the mechanical problem admits ; or the
ether may be contemplated as a piece of mechanism specially
adapted to its work.

SECTION XIV.

115. Constitution of the Ether ; Physical Belations. — ^There are
some extremely simple relations between the mean length of path
of the particles of an aeriform medium, the mean distance of the
particles, and the dimensions of the particles. Clausius, who has
investigated this subject, and who applied his results specially to
gases, has established, mathematically, a relation as regards the
mean length of path of a gaseous molecule, which, applied to the
case of the ether, would be as follows : The mean length of path
of an ether particle is in the same proportion to the radius of the
particle (supposing it to be spherical) as the unit volume of
space is to the volume of matter contained therein, i.e. the
total volume of the particles contained in this unit volume of
space.

Since the volume of matter is directly proportional to the
number of particles, the theorem might be otherwise stated, viz.
that the mean length of path of a particle is greater in direct
proportion as the number of particles (of given size) is less. This
fact will become tolerably evident on consideration of the subject,
for it is clear that the mean length of path, or the distance that a
particle can move without obstruction by other particles of the
medivm, will depend on the number of these obstructing particles,

79

the mean length of path of a particle being greater as the number
of obstructing particles is less.

It may be further shown to be a result of the above theorem,
that the relation between these values, i. e. the values of the
mean length of path, mean distance, and the radii* (or diameters)
of the particles of an aeriform medium, is constant, whatever the
state of subdivision of the matter forming the medium. Now, it
is at first evident that the volume of matter cannot be afifected by
subdivision of the matter, and therefore the relation of the mean
length of path to tlie radius of the particle, which depends directly
(as in accordance with the theorem) on the volume of matter,
cannot be afft3cted by subdivision of the matter ; so that, therefore,
the ratio of the mean length of path to the radius of the particle
will remain constant, whatever the state of subdivision of the
matter of the medium may be conceived to be. If, therefore, we
were to imagine a progressive subdivision of the matter of the
medium to go on, the radius (or diameter) of the particles and
the mean length of path would diminish in precisely the same
ratio, the two, therefore, preserving a constant ratio to each other.

It only remains to show that the relation of the mean distance
of the particles to these other values also remains constant, what-
ever the state of subdivision. We may imagine (according to the
proceeding adopted by Clausius) space to be subdivided into a
number of small cubes, and that at each comer of all these cubes
a particle is placed ; then any side of a cube will represent the
distance of the particles, or the mean distance when the particles
are placed irregularly, or are in motion. Now, it will be apparent,
on considering the question, that by subdivision of the matter of
the medium, the side of any one of these cubes and the diameter
(or radius) of the particle will diminish in the same ratio. Thus,
to take any case : if we suppose by the process of subdivision the
diameter of each particle to be halved, then the volume of each
particle is thereby reduced to one eighth (the volume of a sphere
being as the cube of the diameter), and, therefore, there is now
matter available for eight times as many particles ; and accordingly,
therefore, space may now be further subdivided into eight times
as many small cubes, at the corners of all of which particles may
be placed. But by this process it will be observed that the side
of the cube (i. e. the distance of the particles) has become pre-
cisely halved, the length of the side of any one cube being
inversely as the cube root of their number. The effect, therefore,
of reducing the diameter of the particle to one half by the
imaginary process of subdivision of the matter has been to reduce
the mean distance to one half; and, therefore, the relation of the

♦ In the case of the molecules of a gas, radii^ would mean " radius of sphere of
action " (as termed by Clausius), i. e. the mean radial distance within which vibrating
gaseous molecules, separated by the ether, approach in their mutual interchange of
motion.

80

Pia. 8.

mean distance of the particles to the diameter has been unaffected
by the subdivision.

It follows, therefore, that whatever the state of subdivision of
the matter of an aeriform medium may be conceived to be, the
values of the mean length of path of the particles, the mean dis-
tance of the particles, and the diameter of the particles, preserve
a constant ratio to each other, and therefore the proportionate (or
relative) values would be determined by a knowledge of the pro-
portion of space to matter contained therein, also a determination
of any one of these values in absolute measure would determine
all. It may be observed that the proportion of space to matter in
the medium is evidently proportional to the density of the medium.

There is, accordingly, no limit to the smallness that the values
of the mean length of path, mean distance, and diameter of the
particles may attain by subdivision of the matter of the medium,
all of these values diminishing indefinitely, and preserving a
constant ratio to each other as the subdivision progresses.

116. The mode in which these values vary by the process
of subdivision of the matter of the medium may be represented

graphically in a simple manner.
Thus, in the diagram (Fig. 8), if
the ratio to the line /s to half an
(radius of particle) represent the
ratio of the unit volume of space
to the volume of matter contained
therein, in the case of the medium,
then the lines fs and s n will repre-
sent the proportionate values of the
mean length of path and the dia-
meter of the particle. If s?* and
Iff represent any two particles of
the medium, the line joining their
centres (i. e. the prolongation of the
line fs) will represent the mean*
Then if lines be drawn from these
points to a common point p, any straight line (such as the line
/' ff') drawn parallel to fff, anywhere between it and the point
Py will at its points of intersection represent the values of the
mean length of path, mean distance, and diameter of the particles,
corresponding to another state of subdivision of the matter of the
medium (the parallel straight lines being cut proportionally);
these values diminishing indefinitely, and at the same time pre-
serving a constant ratio to each other, as by the progressive
subdivision of the matter of the medium, the line fff advances
towards the point p.

117. The relation of the mean length of path of a particle of

* The proportionate value of the mean distance is here given somewhat too great,
far convemence in the diagram, the principle involved not being affected thereby.

-**

distance of the particles.

81

an aeriform medium to the radius of the particle being in the
relation of the volume of space to the volume of matter (i. e. pro-
portionate to the density of the medium), the known low density
of the ether, therefore, makes the influence neceasary that the mean
length of path, and even the mean distance of the particles, must
be a large multiple of their diameters ; but on this account the
absolute values of the mean length of path and mean distance
need not be large, but by the simple condition of subdivision of
the matter of the ether, these values may be reduced without
limit ; as in the illustrative diagram, by the process of subdivision
and the attendant reduction of the diameter of the particles, these
particles would gradually advance (or slide between the inclined
lines) indefinitely near to the point jp, carrying the line fg repre-
senting the corresponding values of the mean distance and mean
length of path, along with them, all the values therefore approach--
ing the vanishing point as the subdivision of the matter of the
medium progresses.

The admirable appropriateness of this mathematical relation
as a mechanical condition to render practicable the existence of an
intense store of energy, and its necessary accompaniment an
intense pressure, will be apparent. For the simple condition of
an extremely subdivided state of the matter of the medium not only
renders a high speed practicable to the particles, by reducing the
energy of each almost up to the vanishing point, but this condition
has also the eflfect of curbing the motion within almost infinite-
simal limits, and of reducing the mean distance and multiplying
the number of particles to such a degree that the equilibrium of
pressure even about the small mass of a molecule becomes prac-
tically perfect ; and therefore the existence of a pressure of an
extreme intensity becomes quite practicable, without disturbance
of the equilibrium of the molecules of matter, and the consequent
concealment of the pressure from the senses becomes complete.

By the reduction of the mass of the particle and the attendant
reduction of its mean length of path as a result of subdivision, not
only does the energy of each particle taken separately become
vanishingly small even when the particle is moving at the speed of
light, but the limits of its path almost vanish ; or if we regard
the limits of path of each particle, the particle might as well be
at rest as far as any power of appreciating the limits of its path by
the senses is concerned, and yet by the multiplicity of particles
attendant on the extreme state of subdivision, and by the conse-
quent addition of the paths of the innumerable particles in their
interchange of motion, a wave advances at the speed of light
without the motion of the physical links of the chain being appa-
rent; and although by subdivision the energy almost vanishes
when each particle is regarded separately, yet the total energy
exists to its full intensity.

82

SECTION XV.

118. The Interchange of Motion in the Locomotive. — We may, as
a good illustration, briefly consider the processes involved in the
interchange of motion taking place in the locomotive engine.
We will regard the state of the case at the point when the steam
has been just freshly turned on ; then at that instant the molecules
of steam, previouslv in motion and rebounding from each other
and from the closed valve of the steam pipe, move along the pipe
with their normal velocity on the valve being opened, and imping-
ing against the pistons, transfer part of their velocity to the latter,
causing the propulsion of the engine. The loss of motion thus
sustained bv the steam molecules next the piston is transmitted
backwards m the form of a wave, by interchange of motion from
molecule to molecule into the steam space of the boiler, the
transmission of the wave (or decrement of velocity) being the
necessary consequence of the exchange of motion going on among
the steam molecules, the rate of transmission of the wave being
that of the molecules themselves. This loss of motion, therefore,
next affects the surface molecules of the water, and the water thus
chilled sinks downwards, thus transmitting the loss of motion to
the molecules of the metallic casing forming the heating surface
of the boiler. The loss of motion thence passes to the molecules
of the fuel next the metallic casing, or the loss of motion is sustained
by the store of motion in the furnace, and since the ether is the
motive agent of the molecular motion of the fuel, every decrement
of motion sustained by the molecules of the fuel is a decrement
sustained by the ether, the decrement sustained by the fuel
having been previously supplied by the ether, and in this way,
therefore, the loss of motion is brought to bear upon the source of
motion, the ether.

If this included all the points of the process, therefore, the loss
of motion sustained by the molecules of the fuel might have
been supplied to these molecules some time previously, the
motion having existed in the interval as a store motion in the fuel,
ready to be given up at any time. If this, however, were the pre-
cise state of the case, the supply of motion by the ether would
necessarily be wholly independent of the withdrawal of this motion
from the fuel, or the two processes would go on quite indepen-
dently of each other ; and if this were the case, the amount of
motion supplied by the ether to the fuel would be quite indepen-
dent of the fact, whether this motion was utilized (expended) or
not, i. e. the ether would continue to supply motion quite inde-
pendently of the fact whether there was a demand for motion or
not Now, it may be shown that this is not the actual case, but

83

that by a special process the supply of motion by the ether
becomes to a certain extent adjusted to the demand, or a rapid
drain of motion from the fuel (i. e. from the freshly combined
molecules of carbon and oxygen) brings the ether into augmented
action, and when there is no demand for the motion of the fuel
the energy of the ether is held to a certain extent in reserve. In
order to follow this process we must consider certain points.

119. It is a known fact that an elevation of temperature
beyond a certain degree tends to separate chemically combined
molecules (and, indeed, molecules generally), and by a due eleva-
tion of temperature the molecules are completely separated (** dis-
sociated"), or an excessive degree of vibrating energy is un-
favourable to the stable union of the molecules, or, as before
alluded to, a certain degree of vibrating energy exists which is
the best adapted to effect a reduction of the ether pressure
between the molecules, causing them to approach with maximum
energy. When, therefore, the temperature of combined molecules
is raised beyond the point which corresponds to the maximum
stability of their union, the molecules commence to recede from
each other, the molecules at last separating completely at the
temperature of dissociation. When, conversely, the temperature of
molecules is beyond the temperature of dissooiation, a lowering
of the temperature may be followed by a combination of the mole-
cules, the molecules afterwards gradually approaching into closer
proximity as the excessive vibrating energy is gradually reduced.

Thus, if we take, for example, the case of the combination of
the constituent molecules of carbon and oxygen to form a com-
pound carbonic acid molecule in the combustion of coal, then the
high velocity with which the pair of vibrating molecules in their
approach are driven against the intercepted oscillating ether
column intensifies so greatly the vibrating energy of the column
that the molecules are temporarily checked by their own rapid
approach; and as the excessive vibrating energy is gradually dis-
sipated in the surroimding ether, the molecules gradually approach
into closer proximity. But this approach of the molecules, in
which act the pair of vibrating molecules are slowly urged by the
ether pressure against the intercepted vibrating ether column, is
necessarily attended by fresh increments of vibrating energy in
the molecules, so that, in fact, the molecules cool more slowly than
would otherwise be the case; and instead of all the vibrating energy
(heat) being developed and concentrated in the first act of approach
of the molecules, a part of the heat is subsequently generated; but,
as an important point, this subsequent generation of heat is entirely
subject to the condition that the heat first generated is drawn off
or utilized ; for unless this be the case, i. e. unless the vibrating
energy of the molecules change (by the loss of heat), the molecules
will necessarily remain at a fixed distance from each other, suited
to their special degree of vibrating energy, and the moleculea

84

would not approach into closer proximity at all unless their vibrating
energy were changed, i. e. unless their heat were drawn off; so
that, therefore, by the absence of demand for heat, the energy of
the ether is held in reserve ; and conversely, by a rapid drain
upon the heat, the molecules would rapidly take up their final
positions of proximity due to normal vibrating energy, and thus
the ether, by urging the vibrating molecules into closer proximity,
foUows up the demand for heat by a fresh supply.

120. By this special process the work of combustion is greatly
equalized, and instead of the intense initial heat that would result,
were all the heat developed in the first instant of combination oif
the molecules, the initial heat is moderated, and the development
of heat equalized by being spread over a certain period of time.
By this process the action of combustion, as in the case of the
locomotive, for example, is brought to bear against, or is spread
over a larger surface, and instead of all the heat being concen-
trated to an excessive amount in the furnace itself, which would
possibly be detrimental to the constructive materials, a portion
of the heat Is generated in the tubes of the boiler, or an incan-
descent carbonic acid molecule in its progress through the tube
develops fresh increments of vibrating energy, by the gradual
approach of its pair of components under the action of the ether,
as the vibrating energy of tnese components is gradually expended
in the progress of the molecule through the tube. The compound
molecule forms, therefore, an extremely sensitive piece of mechanism,
the slightest change of temperature (change of vibrating energy)
causing a readjustment of the distance of its pair of components
relatively to the intercepted vibrating ether column, whereby the
ether comes into fresh action.

From these considerations it would also follow that the escape
of products of combustion at a high temperature is not only
wasteful On account of the absolute heat being thus lost, but also
on account of the fact that the additional heat generated as the
lowering of the temperature proceeds is also lost.

The turning on of the steam in the case of the locomotive,
followed by the continued chilling of the extensive surface of the
flue-tubes by the continued evaporation of the water as the engine
proceeds, therefore brings the ether into fresh action in the flues,
whereby combustion is more complete than would otherwise be
the fact, and thus the demand for heat by a seK-acting mechanism
brings the ether into action, causing a fresh supply.

121. We may perhaps just note here, in connection with this
subject, that this special deportment of aggregated molecules
admits of being illustrated by a case in which the effect is actually
visible. For the effect to be visible it is clearly only necessary
that the molecules should be aggregated in sufficient numbers as
to multiply the effect of each pair of molecules, and thereby render

the effect visible. Thus the abstraction of heat from a heated bar

85

of metal, for example, is followed by a closer approach of each
pair of molecules forming the bar (the contraction of the bar being
measurable) under the action of the ether, whereby each pair of
vibrating molecules is slowly but forcibly urged against the
oscillating ether column intercepted between them, a fresh de-
velopment of vibrating energy in the molecules being the result,
or more heat must be abstracted from the bar in order to lower
its temperature to a given degree than if the bar did not contract
(i. e. if its molecules did not approach), this additional quantity of
heat being precisely that developed by the ether in effecting the
approach of the molecules. The effect is of course relatively
feeble here compared with the effect in the case of the more
intimate grouping of dissimilar molecules about a common centre
to form compound molecules (chemical union), the effect being
greater in proportion as the energy of chemical combination
is greater, and also in proportion as the range of temperature to
which the molecules are exposed is greater. Thus, to form a just
appreciation of the effect in the illustrative case given of the loco-
motive, we must take into account the energy of the approach of
molecules in combustion, and also the extreme range of tempera-
ture to which the products of combustion are exposed.

It may also be observed that in a perfectly analogous manner
the aggregated molecules of the metallic bar may be dissociated,
or completely separated, by a due elevation of temperature.

122. In the interchange of motion taking place in the locomo-
tive, it forms a point of interest to observe how in niechanical
conformity velocity is apportioned to mass, or we have the
extremely rapid motion of the minute ether particles, the slower
motion of the larger masses constituting the molecules of coal and
steam, and the still slower motion adapted to the large masses
forming the visible part of the mechanism. Also the transference
of motion takes place step by step by a gradual process, the
motion passing first from the minute but rapidly-moving ether
particles to the relatively large masses of the molecules of coal,
the motion passing thence through the intervention of the mole-
cules of steam, to the massive and slowly-moving pistons.

In the inverse process by which the motion is returned to the
ether, or to its original source, the transference of motion takes
place in the same gradual way, the motion passing from the
massive moving parts of the engine to molecules, as represented
by the heat developed in the working parts, the motion passing
from these molecules to the ether in the form of waves (by radia-
tion). The escaping steam and gaseous products of combustion
whose residual motion has not been transferred to masses, lose this
motion by transference to the ether ; and thus the motion derived
from the ether is being continually returned to the ether during
the progress of the engine. The process involved is therefore a
cyclical one, consisting in the transference of motion from the ^

86

ether through matter to the ether; or the process involved in
the case of the locomotive, viewed fundamentally, consists in the
ingenious disposal of a train of matter under such physical con-
ditions that tnis train of matter takes motion from the ether at
one end and returns the motion to the ether at the other end. A
fundamental principle of extreme simplicity, therefore, underlies
the complexity of the mechanical arrangement.

123. It is a very firmly grounded idea that simplicity should
exist in the working of physical phenomena, or that physical
processes should be simple. Now, although the existence of this
simplicity is an undoubted fact proved by experience, the exist-
ence of a strict cause for this is not perhaps so generally recog-
nized. Without attempting at all to go fully inU) this question,
we think that at least one determining cause for this simplicity
may be pointed out. A physical process resembles, and indeed
may be defined as, a mechanical process. Now, in all the me-
chanical processes of industry, as in constructive mechanics, or in
any case whatever where a mechanical means or adaptation is
applied to an end, simplicity is actually recognized as the
governing principle. The whole aim of constructive mechanism
is directed towards simplicity, as in the case of the locomotive,
for example ; the advance towards simplicity constitutes one of
the main stages of its progress. The real fact is, that the end is
not otherwise attainable except under the condition of simplicity,
for if a mechanical adaptation or machine be not simple, or if it
have more parts than are absolutely essential to the intended
purpose, the machine will not fulfil its intended purpose, i. e. it
will not perform its functions in a proper and orderly manner.
To have, therefore, order in the working of any mechanical process,
or means to an end, simplicity may be said to be a necessary
condition. If, therefore, order be observed to exist, the existence
of simplicity may be deduced therefrom. It is, therefore, not
a mere question as regards superfluity, or that simplicity is
desirable because superfluity would be in vain, but the end is not
attainable at all excepting under the condition of simplicity. It
would follow from these considerations that simplicity in physical
phenomena may properly be regarded as the absolutely necessary
condition to the attainment of the observed results, or as the
essential condition to the proper and orderly working of physical
phenomena.

In the case of the locomotive, for example, simplicity, or no
superfluity of parts, must be as essential to its molecidar me-
chanism (i. e. the mechanism of the coal, ether, and steam) as to
its larger scale mass mechanism, for mere dimensions or size
cannot affect the principle evolved, the larger scale mass me-
chanism being itself composed of the very same parts of which the
molecular mechanism consists, for the mass mechanism is all made
up ofmoleculea surrounded by the ether. Hence we may expect

87

to find simplicity and no superfluity of parts in the molecular
mechanism of the locomotive ; nevertheless it is just as essential
that this mechanism of the vibrating molecules of coal and the
ether, with their mutual interchange of motion, should have con-
nected parts and should form a connected whole, as that the
larger scale mass mechanism should have connected parts and
should form a connected whole, for the principle of reasoning
and the method of viewing the subject cannot in any way be
affected by a change of dimensions of the mechanism. The mole-
cular mechanism of the locomotive, minute in detail but vast as a
whole, may indeed be regarded as the main part of the mechanism,
for there the motion originates. The mere outer shell and appli-
ances of the locomotive without the mechanism of the action of
the ether upon the vibrating molecules of co^,l, might be compared
to the outer shell of a flute with its arrangement of keys without
the hidden mechanism of the air, which by its stationary vibra-
tions in columns of varied length is the real source of the sound,
the outer shell of the flute fulfilling a purely subsidiary part.

It might also have been observed above, in connection with the
subject of simplicity, that the beauty of simplicity consists in its
uniqueness ; for while there are an indefinite number of ways of
attaining a result or mechanical end by a complicated method,
there is but one way of attaining the result by a simple method,
which therefore entails a special exercise of the intellect to
find it.

124. Steam owes its handiness and power as a dynamic agent
to the physical qualities of a rapid motion of its component
mplecules combined with lightness (i. e. small quantity of matter
relatively to the unit volume of space) ; and just as these special
physical qualities exist developed to a far higher degree in the
case of the ether, so the ether is by so much superior to steam as
a dynamic agent. Steam evidently cannot be looked upon as a
true dynamic agent or source of motion, since steam only becomes
a dynamic agent after the motion to be utilized has been
imparted to its molecules. The ether, on the other hand, is a
true dynamic agent or source of motion, since the ether in its
normal state already encloses a store of motion. In the case of
the locomotive, therefore, the motion cannot be said to be derived
either from the steam or the coal, since the former is not a
dynamic agent, and the coal has no motion to impart. The
motion can only be derived from a source where motion exists, i. e.
from the ether, whose normal state is a state of motion ; the coal
and steam simply forming convenient pieces of intervening me-
chanism by which the motion of the ether is transferred to the
pistons, just as the connecting-rod, for example, is the convenient
piece of mechanism by which motion is transferred from the
pistons to the wheels.

125. The Energy of Combustion. — It is a known fact that the

88

dynamic value of the combustion of one pound of coal (darbon)
amounts to about eleven million foot-pounds. From this it may
be computed that the intensity of the energy developed at the
combustion of coal is such that it would be competent to proiect
the mass of coal and oxygen taking part in the process to a height
of not less than 570 miles.

Now, regarding this remarkable fact as any other mechanical
question or engineering problem, and with the view to form a
practical realization of the means by which this result is attained,
or the mode in which this amount of energy can be brought to
bear against the coal, such as the coal filling the furnace of a
locomotive, for example, it is well to keep practically in view the
important peculiarity of the molecular state of matter, by which a
vast extent of surface is brought under the dynamic action of the
ether, the ether pervading the entire mass of coal which fills the
furnace, and surrounding each one of the innimierable molecules
of the mass. If we take a single cubic inch of coal and imagine it
spread out into a layer, one molecule in thickness, some idea may

{lerhaps be formed of the amount of surface that must be exposed,
f we suppose that a carbon molecule would be contained within
the limits of nr. ooo . ooo inch, then such a layer of coal would cover
upwards of one acre and a half. This estimate is merely intended
to give a rough idea of the vast extent of surface that must be
exposed, the estimate being probably less than the actual fact,
since the above assumed value for a molecular dimension is almost
beyond question too great.

If, therefore, this represent the surface exposed by a single
cubic inch of coal, what must be the vast extent of surface exposed
by the mass of coal which fills an ordinary locomotive furnace?
If we figure to ourselves this vast extent of surface brought under
the play of the intense ether pressure, or these innumerable
molecules of carbon brought under the intense dynamic action of
the ether which pervades the furnace, then the intense energy of
combustion will reconcile itself with ordinary mechanical prin-
ciples, and even become a necessary deduction following these
principles.

126. Movements of Animals. — It is a recognized fact that a
fixed relation exists between the movements of the animal body
or the work performed, and the chemical processes taking place
within the animal system, the work performed being the exact
mechanical equivalent of the energy developed at the oxidation of
the food ; the animal system in this respect, therefore, precisely re-
sembling a mechanical motor, such as the steam engine, for example,
where the work performed is the exact mechanical equivalent of
the energy developed by the combustion (oxidation) of the coal,
including of course under total work, in both cases, the attendant
dissipation of a portion of the energy in the form of heat.

The ether being the physical agent concerned in chemical pro-

89

cesses generally, whether in the oxidation of the food in the case
of the animal Dody, or in the oxidation of the coal in the case of
the steam engine, the ether therefore must constitute the original
source of motion in the case of the animal system, as in the case
of the steam engine, and that of mechanical motors generally.

In a perfectly analogous way the entire work done hy the
animal system goes in its final stage to the ether (in the form of
waves of heat, &c.), i. e. to its original source in a cyclical process.
However complex and varied, therefore, the molecular processes
and changes may be which take place within the animal system in
the passage of the motion through its intermediate stages, and
however difficult it may be to follow the motion through the entire
cycle, it is none the less certain that the ether is the primary
source and final receptacle of the motion.

SECTION XVI.

127. The Identity of Physieal Processes in their Fundamental
Naiv/re. — We have observed that all physical processes are iden-
tical in one fundamental respect, in that they all consist in an
interchange of motion. The interchange of motion may therefore
be said to constitute the simple groundwork or fundamental
principle upon which all physical phenomena in their vast variety
are based, and in this one circumstance the necessary correlation
of all branches of physical science lies apparent. The fundamental
principle is itself simple, yet, from its very nature, consistent with
the production of phenomena of endless variety. The interchange
of motion may be said to form the whole basis of the great prin-
ciple of conservation^ for the very idea of the interchange or
transference of motion itself precluaes all idea of the possibility of
the annihilation of motion ; or the only possible method of getting
rid of the motion of a mass of matter is by transferring that
motion to another mass or masses.

128. We shall now proceed to consider more closely the mode
or general principle upon which physical processes effect them-
selves, and it will be our endeavour to show that these processes
resemble one another in a second fundamental aspect, viz. that all
these processes are cyclical, i. e. consist in a transference of motion
from the ether through matter to the ether, or consist in a trans-
ference of motion from and to the same source ; and therefore that
all physical processes, however diverse and varied, are identical in
this fundamental respect ; or that every observed motion whatever
came from the ether at one time, and will return to the ether at
some subsequent time.

90

This theorem may be shown to be a necessary consequence re-
sulting from the fundamental principle of conservation. The normal
state of the ether is a state of motion, or the component particles of
the ether transfer their motions among themselves, and this motion
is of necessity permanently maintained. The ether, therefore, con-
stitutes a source of motion. A mass or molecule of matter, on the
other hand, cannot possibly be in motion without continually
giving up some of its motion to the surrounding ether, which
motion is rapidly carried ofiF to a distance in the form of waves ; so
that matter cannot possibly remain in motion, unless the motion
be renewed by the ether as rapidly as it is being dissipated in the
ether, which would constitute a cyclical process. Since, therefore,
the motion of matter is being continually dissipated in the ether,
the ether constitutes the receptacle of all the motions of matter.
The ether therefore must, in accordance with the principle of
conservation, be the source of all the motions of matter, for matter
cannot evolve motion out of itself. Also, since matter cannot
retain its motion, but must be always dependent on the ether for
any supply of motion, matter therefore cannot in any case consti-
tute a source of motion. The ether therefore constitutes both the
source and the receptacle of all the motions of matter, or this
would constitute the theorem that all physical processes are
cydicaly or consist in a transference of motion from and to the
same source, and accordingly that all physical processes are corre-
lated in this fundamental respect.

129. It is obviously not necessary that all motions should come
direct from the ether, but an observed motion may have been
transmitted through matter since its original derivation from the
ether. Thus, for instance, there may exist a store of motion
originally developed by the ether in matter, and from this store of
motion the observed motion may directly come. The sun, for
example, constitutes such a store of motion. Any observed motion
of a mass or molecule, therefore, traced backwards in the first
instance to the sun, is simply a motion which in its passage from
the ether to the ma^s or molecule has been transmitted through
the sun as an intervening link in the cyclical process, the motion
afterwards passing from the mass or molecule to its original source,
the ether.

Again : it is quite evident that an observed motion need not
pass to the ether direct, but this motion may undergo several
transferences through matter first. But it is clear that such a
process must have a limit, for any attempt to retain motion in
matter, or to prevent the passage of the motion to the ether
by transferring the motion from one mass or molecule of matter
to another, would only render the passage of the motion to the
ether the more rapid, for during the whole process, and more
especially at every such interchange of motion between masses
and molecvleBf a portion of the original motion is necessarily

91

dissipated in the ether in the form of waves of heat. In tracing,
therefore, conversely, a motion backwtirds, there is a distinct limit
to the number of times this motion can have been transferred
through matter, for the number of transferences a motion can
undergo without complete dissipation must be limited by the
original value of the motion. Hence, although a motion, observed
at any point of its progress, may have undergone several trans-
ferences through matter since its original derivation from the
ether, and this motion may in certain cases undergo several such
transferences before passing finally to the ether, the process is
nevertheless in all cases a cyclical one, or the motion comes from
and passes to the ether.

130. We shall now refer to some practical examples illus-
trative of the above theorem. The main adaptations for the
derivation of power may be classed as steam, the utilization of
the fall of water, the utilization of winds, and the work of animals.
In all these cases the physical processes involved may be shown
to be identical in principle, or the processes are cyclical, con-
sisting in the transference of motion from the ether through
matter to the ether.

In the case of the steam engine and the animal system,
already treated of, the energy derived from the ether in the
combustion (oxidation) of the coal and food in the two cases,
passes to the ether in the various operations performed, the with-
drawal of motion from the ether and its transference to the ether
going on simultaneously.

131. The " fall " (approach) of masses (" gravitation ") re-
sembles the approach of molecules as regards the physical process
involved. When, therefore, the fall of water is utilized for mecha-
nical purposes, the motion developed in the water is derived direct
from the ether, and is transmitted by the wat^r through the
machinery to the ether (in the form of waves of heat developed
in the working parts of the machinery, &c.), the process involved
being a cyclical one, in which the derivation of motion from and
its transference to the ether go on simultaneously.

132. The production of winds may be referred in general to
the adjustment of differences of pressure in the atmosphere, these
differences of pressure having been brought about by differences
or changes of temperature. This adjustment of differences of
pressure being directly due to the action of gravity, the motion of
the current of air and of the current of water may therefore be
brought imder the same physical cause, i e. the direct action of
the ether. By the utilization, therefore, of winds for mechanical
purposes, the air current forms the convenient mechanical adapta-
tion by which the motion of the ether is transmitted to the
machinery, the motion passing in the various operations of the
machinery to the ether in a cyclical process.

In regard, therefore, to the four principal means for the deriva-

92

tion of power, viz. steam, currents of water, currents of air, and
the work of animak, the physical processes involved may be all
classed as identical in pnnciple, the processes being cyclical^ con-
sisting in the simultaneous withdrawal of motion from and its
transference to the ether.

133. The formation of coal was due, as is known, to the action
of the sun's rays upon the molecules of carbonic acid, by which the
components of the compound molecules were separated, the carbon
being deposited in the vegetation, becoming eventually the food
of the animal and the fuel of the steam engine. At the separation
of the molecules, therefore, by which the carbon was deposited, the
work was done by the ether waves (sun's rays) on the ether, or the
amount of motion lost by these waves was equal to the amount of
motion imparted to the ether in the process of separating the
molecules, and in which the work of separation consisted. In this
case, however, the ether could not be said to be, at the time, the
source of the motion which separated the molecules, since at the
time of separation the ether was only the transmitter of that
motion from the sun ; and therefore this case is in one respect
different from the reverse case of the approach of the molecrules
(combustion), when the ether is, at the time, the source of the
motion of approach of the molecules, or the derivation of motion
from and its transference to the ether go on simultaneously.
The ether was, nevertheless, the source of the motion which sepa-
rated the molecules, or the process formed a cyclical one of the
special character already treated of, i. e. a cyclical process in
which the motion derived from the ether has, in its passage to the
molecule, been accumulated in the interval as a store of motion in
matter ; or the ether, as the original source of the sun's heat, was
thereby the source of the ray which separated the molecules, the
separation of the carbon molecules at the production of coal having
therefore formed part of a cyclical process, in which the develop-
ment of the sun's heat formed an intervening link.

Precisely the same considerations apply to the case of the eleva-
tion (separation from the earth) of the molecules of water, under
the action of the sun's rays, to form eventually water currents
(streams) ; and to the case of the elevation of the molecules of air
under the action of the sun, to form eventually air currents
(winds) ; or the process involved in the elevation oi the molecules
in the two cases is a cyclical process, in which the motion in its
passage from and to the ether was accumulated for a period in
matter (the sun) as a store, and therelbre the derivation of the
motion from and its transference to the ether are necessarily not
simultaneous,

134. As regards, therefore, the separation of the molecules of
carbon which deposited in the vegetation becomes, in the form of
animal food and coal, an adaptation for the derivation of power in

two important cases ; and as regards the elevation of the mole-

93

cules of water and air, which also become adaptations for the
derivation of power, the physical processes involved in all these
cases are identical in principle among themselves, or the processes
are all cyclical, in which, however, the motion derived from the
ether has been accumulated as a store in matter during its passage
from and to the ether ; and therefore the derivation of the motion
from and its transference to the ether do not take place simul-
taneously.

On the other hand, the physical processes involved at the
derivation of the power, i. e. at the oxidation (combustion) of the
carbon in the animal system and in the steam engine, and at the
movement of the molecules of air and water in the form of winds
and streams, are also cyclical processes, identical among them-
selves, but in one respect different from the previous processes,
in that the motion comes direct from the ether at the time, or
the transference of motion from and to the ether goes on simid"
taneously.

SECTION XVIL

135. Amomd of energy hdng dependent on the quantity of
matter in motion and on the square of the velocity of motion, and
since motion cannot come into existence spontaneously, or go out
of existence spontaneously, but in accordance with the principle
of conservation, the sum of energy must remain constant; it
follows, therefore, that whenever there is a loss of motion by
matter, there must be a simultaneous gain of motion by matter,
or the loss and gain of motion must be simultaneous, for a loss of
motion without a simultaneous gain of motion would involve for
an interval of time an annihilation of energy.

It follows, therefore, as a necessary consequence from this, that
the energy expended in any physical process whatever can be
solely dependent on and due to motion simultaneously imparted,
i. e. imparted at the time of the expenditure of the energy ; for
imless motion be imparted at the time, energy cannot be expended
at all, for to expend motion without imparting motion would be to
annihilate energy ; indeed, the motion imparted is itself the
measure of that expended, and is the sole cause of its expendi-
ture, i. e. motion can only be expended in the communication
of motion, and in that fact lies apparent the principle of the
Indestru/dihility of Motion.

136. Physical processes accordingly consist in an interchange
of motion. " Work," which admits of but one definition, consists,
therefore, in every possible case in the communication of m>otion^
When the object is to check motion, a ** resistance " is applied. A

94

" resistance " has but one character, and consists in a means or
adaptation for the transference of motion. It may serve, therefore,
well to illustrate the principle of the indestructibility of motion,
to note the fact that the very means applied to extinguish motion,
or a " resistance " itself, is a direct means for communicating
motion, or the only possible means of getting rid of motion is by
communicating motion. The most effective railway brake, for
example, is that through which, in a given time, the greatest
amount of motion is communicated in the form of molecular
motion (*'heat").

137. Beverse Processes. — Since the amount of energy expended
in any physical process is solely dependent on the amount of
motion imparted at the time of the expenditure of the energy, it
follows that the amount of energy interchanged in any physical
process can have no necessary connection with the amount inter-
changed in another process, but the amount of energy interchanged
in any physical process is dependent solely on the physical
conditions involved in that process. Whether, therefore, two
physical processes happened to oe equivalent to each other or not
would depend on the physical conditions involved in each.

In reverse physical processes generally, i. e. by the approach
and recession of masses and molecules of matter, there is an obvious
general similarity in the physical conditions, since the masses and
molecules in the two reverse processes traverse precisely the same
path, imder the same circumstances. Hence it would be reason-
able to expect a certain equivalence to exist in the quantities
of energy interchanged in the two processes. There is, nevertheless,
one important exception to the similarity of the physical
conditions which we shall consider. Thus, for example, in the
case of chemical decomposition and recomposition, when two
vibrating molecules are moved from each other, the ether which
resists the motion and upon which the work is done, is necessarily
to a certain extent condensed, by an amount dependent on the
velocity of recession of the molecules. Owing, therefore, to the
condensation, the number of particles to which motion is imparted
is correspondingly increased, and accordingly the work done in
separating the molecules is increased from this special cause. On
the other hand, when two molecules are urged towards each other,
the ether which does the work is (conversely) to a certain extent
rarefied, since the movement of the molecules takes place in a
direction from the portion of the ether which does the work. The
number of particles in action being thereby reduced, the work
done at the approach of the molecules is thereby reduced. Since,
therefore, this special physical cause acts conversely in the two
reverse processes, or contributes to increase the energy to be ex-
pended at the separation of molecules, and to reduce the energy to
be derived at the approach of molecules, and since, however slowly
tie motion of the molecules might take place, this physical cause

95

miist have its corresponding eflTect, it follows, therefore, that in
mathematical strictness two reverse physical processes never can
be equivalent. The degree of nearness of approach to actual
equivalence would depend upon the relation existing between the
normal velocity of the ether particles and the velocity with which
the movements of matter in the reverse processes take place.
Since the ether particles happen to have a high velocity, and
the movements ot molecules in chemical action are in no case
comparable to the noimal velocity of the ether particles, the
two reverse processes must therefore approach nearly towards
absolute equivalence, or the difference is not sufficient to have
made itself observable. The accumulated differences of such
processes, however, by continual repetition, in course of time must
reach an important amount. The most likely case to attract the
observation would be one where the motion takes place at a high
speed and over long distances, as, for example, in the case of
cosmical matter propelled by the action of the ether in " gravi-
tation," where, on account of the long-continued action through
great distances, the final speeds attained are much greater than in
the case of molecules propelled by the action of the ether in
" chemical action." It is a significant fact that comets in their
alternate swing of approach and recession from the sun in their
eccentric orbits, lose velocity, and shorten their paths by palpable
amounts.

138. If by any device the performance of work on the ether
at the recession of molecules could be avoided, then no expenditure
of energy would be required in separating the molecules ; just as,
conversely, if the action of the ether at the approach of molecules
could be prevented, no energy would be derived from the approach
of molecules.

It is well to observe that the work done on the ether at the
separation of molecules is completely useless work, serving no
practical object whatever, since the motion thus imparted is carried
off beyond all power of utilization ; indeed, since whatever means
be used to separate the molecules, whether through the intervention
of heat or chemical agency, the ether (as the motive agent con-
cerned in these two cases) itself does the work of separating the
molecules, or the process is a cyclical one, consisting in the trans-
ference of motion from and to the ether ; it is therefore clear that
it would not affect tlie absolute sum of motion in the least if no
such interchange of motion took place, or if the molecules were
simply caused to recede from each other without the ether coming
into action at all. This is, therefore, not a question affecting in
any way theoretic principle, but simply a question as to the
practicability of a device to avoid the performance of useless
work ; and if such a device were practicable, the components of the
molecules of carbonic acid, for example, would separate without
the performance of work, and the carbon would thus be available

96

to be burnt a second time by the action of the ether. If this
device were practicable, there would no.t be the slightest absolute
gain of motion by it, for a mass of coal or carbon is simply a
machine, and cannot evolve motion independently of a source of
motion, or a mass of coal is simply a piece of mechanism for
utilizing the motion of the ether, just as, for example, a waterwheel
is a piece of mechanism for utilizing the motion of a stream ; or
all the motion developed at combustion, and imparted to the ether
in the form of waves of heat, comes from the ether at the time of
combustion, so that the process of combustion might be continued
indefinitely without the slightest absolute gain of motion, or the
interchange of motion constituting combustion is quite independent
of the fact whether energy was expended in the previous act of
separating the carbon or not. If the vibratory motion of molecules
could be brought under control and thus be temporarily got rid of
by utilization in any way, then the above result would oe attained,
or the molecules would separate without the performance of work;
as we have before pointed out that there are certain considerations
which would indicate that this result is actually attained in nature,
in the disintegration of matter at a low temperature. Thus, for
example, this result is actually attainable in tne case of vibrating
masses where the vibrations arer under control.

If, for instance, we take the case of a vibrating mass, such as a
tuning-fork maintained in vibration by some external source of
power, just as a molecule is maintained in vibration by the ether
waves emitted by the sun ; then, if we suppose a piece of card to
be placed near the fork, and the vibrations of the fork to be
temporarily checked by any means, then the card may be separated
or removed from the fork without the performance of work. If
then, while the card is now at a certain distance from the fork,
the latter be allowed again to vibrate, the card is attracted or
urged towards the fork, and this separation of the card without
the performance of work, and return of the card under the action
of the air, whose moving molecules constitute the source of motion,
might thus be repeated any number of times. Here, by a simple
device, the performance of useless work in separating the card, or
the performance of work in direct opposition to the source of
motion (the air), is avoided. The same considerations applv in
the case of vibrating molecules, the separation of which without
the performance of useless work, or the performance of work in
direct opposition to the source of motion (the ether), is a question
merely depending on the practicability of the application of a
device, and not a question affecting in any way theoretic principle.

139. The motion of a permanent source of motion can always be

made available provided the machinery be applied and used in a

proper manner. The machinery of nature for deriving motion

from the ether all works on the simple reciprocating principle of

approach and recession. A movement of approach must come to

97

an end, so that the problem is to reverse the movement witliont
performing work in direct opposition to the source of motion. By
all the engineering appliances for deriving motion from sub-
sidiary sources, this device for reversing the movement is applied
and recognized as the absolutely essential condition. Thus, in the
case of the steam engine, for example, where motion is derived
from the subsidiary source, steam, a device is applied to reverse
the movement of the piston without performing work in direct
opposition to the source of motion (the steam), and without this
device it would be necessary either to force the piston back in
direct opposition to the steam pressure, whereby the energy
expended would be as great as that derived, or else the piston
would only make one stroke, and then become useless. Now, this
is precisely what is the case with the molecular mechanism of the
steam engine according to the present system of application and
use, or the molecules of coal make one stroke ^approach once)
under the action of the ether pressure and then oecome useless,
and thus, while the larger scale portion of the mechanism of the
steam engine (the mass mechanism) is stationary, or is used again
and again, the molecular mechanism is subject to continuous
renewal, and, in fact, we have the anomaly that the power derived
is proportional to the machinery expended. By the absence of a
device for reversing the movement in the case of the molecular
mechanism, the molecule of carbon must, in analogy with the

Siston in respect to the steam pressure, either be forced back in
irect opposition to the intense ether pressure, or else the molecule
can only approach once, and therefore a separate molecule is
required for every stroke, as in analogy in the case of the larger
scale mechanism, if there were no device for reversal a separate
piston would be required for every stroke. This expenditure of
mechanism clearly cannot aflfect the motive power derived from
the source of motion, but it is inconvenient from the fact that the
stock of coal is not infinite. The simple means of reversal as it
takes place in nature, by dissipation of the vibrating energy of
molecules in the ether by the isolation of matter, cannot be
adopted, since there is no means of isolating matter, and all sub-
stances on the earth's surface are vibrating with intense energy.
Perhaps a partial reduction of the vibrating energy might help,
but we are not restricted to discrete molecules, and possibly the
reciprocating movements of approach and recession of masses
under the action of the ether in the ** electric " and " magnetic "
phenomena might be found more subservient to this special object,
and thus the enormous stores of motion present on all sides be
made of more practical avail than by the present methods of
utilization. At all events, it appears an anomaly that motion
should be only obtainable from a source on the condition of the
expenditure of an equivalent amount of machinery.

98

SECTION XVIIL

140. We may now, as a further practical illustration of the
theorem that all physical processes are cyclical, consider briefly
some of the various industrial operations, or we may take the case
of the varied operations of a steam factory for example. Here,
after the different machines are in full movement, and the work
has assumed its normal value, and there is no further acceleration
or accumulation of motion in matter ; then it follows that fromi
this point the motion must be in the process of being transferred
to the ether as rapidly as it is being derived from the ether. The
test of perfect equality in the motion derived from and given to
the ether is the continued uniform rate of motion of the machines
through which the motion passes in its intermediate stage ; for if
the motion given up to the ether were less than that derived,
there would be an accumulation of motion in matter, or the
machines would be accelerated, the converse being the case if
the motion given up were greater than that derived. Hence,
when the machines are in fall movement the derivation of motion
from and its transference to the ether take place simultaneously
in a cyclical process. It may be noted that at the particular
instant when the machinery was first started, motion was derived
from the ether without being simultaneously transferred to the
ether, this relatively small amount of motion (representing the
motion of the machines) remaining abstracted from the ether so
loDg as the machines are in motion, but when the machines stop,
this motion is returned to the ether (in the form of waves of heat),
the machines coming to rest by converting their motion into heat.

When, therefore, the machinery, including the mechanism of
the coal and engine, is in full action, the surrounding ether must
be simultaneously pervaded by two wave systems ; the one system
consisting on the whole in an excess of motion imparted to the
ether, this system comprising the waves generated in the ether by
the vibrating molecules of matter as a large portion of the motion
derived is converted into heat, including both those waves of
wasted heat, or the motion (heat) which is transferred direct to
the ether by the coal without having previously been transmitted
through the machinery, and the motion of the coal which after
transmission through the machinery is converted into heat in the
mechanical operations taking place. This wave system also
includes, as an important part, the increments of motion given to
the ether particles in the various kinds of work, such as by the
displacement of the molecules of materials, &c. The second of
the two wave systems consists on the whole in a loss of motion
sustained by the ether, as represented by the decrements of
velocity sustained by the particles of the ether as the motive agent

99

of the molecular motion taking place in the boiler furnaces repre-
sented by the combustion of the coal ; the decrement of motion
in the one wave system being precisely equal to the increment of
motion in the other wave system. The quantity of energy in the
ether is therefore, on the whole, neither increased nor diminished
by the progress of the work, but the ether is merely broken up
into waves representing an interchange of motion going on in the
surrounding ether, which is the indication of the interchange of
motion going on in the machinery, which latter forms only an
intermediate b'nk of the complete chain. That the quantity of
energy contained in the ether is unaflTected by the progress of the
work, follows also at once from the principle of conservation in
accordance with which the collective sum of energy contained in
the ether and in matter must remain constani;. So long, therefore,
as the energy of matter represented by the uniform motion of
the machinery remains constant, the energy contained in the ether
must also remain constant, for otherwise the total sum of energy
would be changed. The ether, therefore, being the source and
receptacle of the motion, its component particles are affected by
increments and decrements of velocity, these changes of velocity
being extremely small compared with the normal velocity of the
particles, the ether by the interchange of motion going on among
its particles, tending continually to assume its normal state of
equilibrium of motion, the small changes of velocity being rapidly
carried off in the form of spherical waves, by whose expansion the
changes of velocity are soon dissipated by subdivision.

141. Since work consists in the commtmication of motion, and
since no kind of work consists in the continual accumulation of
motion in matter, it is clear that in every kind of work, as pre-
viously deduced, the motion expended must pass to the ether.
Even if it served any practical end, it would clearly be impossible
to accumulate motion continually in matter, for the greater such
accumulation of motion, the more rapid is its passage to or dissi-
pation in the ether, so that a stage must soon arrive at which the
motion dissipated in the surrounding ether equals that expended.
Accordingly, every possible kind of work will be found, when
analyzed, to consist in the communication of motion to the ether,
either directly or in its final stage. Thus, for example, in all the
varied operations of shaping materials, whatever their nature, such
as the operations of planing, shearing, &c., in which act the
vibrating molecules of substances in stable equilibrium with the
ether pressure are forced out of their positions of equilibrium,
the work consists in the communication of motion to the ether, the
rapid dynamic action of the ether particles entailing a large
amount of work at the displacement of the molecules.

The process of coiling a spring, as by the winding up of a
clock, for example, in which act the vibrating molecules of the
spring are displaced, affords another illustration of work consisting

100

in the commnnication of motion to the ether. If the spring be
coiled through animal agency or through the intervention of a
steam engine, then the motion given up by the ether in transmit-
ting motion through the animal system, or through the mechanism
of the coal and engine, to the molecules of the spring, is equal to
the motion imparted to the ether by the molecules of the spring
in the act of being coiled, or the process is a cyclical one, con-
sisting in* the transference of motion from and to the ether.
Conversely, when the spring uncoils, and communicates motion
to a clock, for example, then the motion expended by the ether
in urging the molecules of the spring bacK into their former
positions of equilibrium, is equal to the motion imparted to the
ether in the K)rm of waves oi heat developed by friction in the
working parts of the clock ; or the physical process is a cyclical
one, consisting in the transmission of motion from the ether
through a train of mechanism to the ether.

Thus all the commonest operations and phenomena occurring
in everyday experience constitute illustrations of the theorem
that all physical phenomena are ftmdamentdlly eorrelated as cyclical
processes consisting in an interchange of motion, and in which the
motion is derived from and passes to one wniversal source of motion,
the ether.

142. Since to develop a given power, the dimensions of a
mechanism such as the steam engine, for example, are less in
proportion as the pressure of the aeriform medium (the steam)
IS greater, and the speed at which the mechanism is worked is
greater ; it would therefore be reasonable to expect, on account
of the extremely high value of the ether pressure and the high
velocitv with which the molecular mechanism for deriving motion
from tne ether is worked, that the total dimensions of this me-
chanism to develop a given power would be exceptionally small.

If we imagine a portion or stick of coal about the size of
an ordinary lead pencil to be ignited at one end so as to burn
away at the moderate rate of twenty grains per minute, then this
little piece of mechanism represented by the ignited end of the piece
of coal would be developing one horse-power under the action of
the ether. Here the pressure of the motive agent is so intense,
and the parts of the mechanism are so beautifully balanced and
curbed by the high elasticity of the ether, that the mechanism
is enabled to work at a high speed, thereby developing an intense
energy by small dimensions. If only this piece of molecular
mechanism could b^ connected up or brought into perfect gear
with mass mechanism, so that the motion was transferred from
molecules to masses without loss, a valuable result would be
attained. Thus in the transmission of motion between the mole-
cular mechanism and the mass mechanism of the steam engine, a
field for improvement evidently exists, in reducing the loss that
at j)resent occurs in the carrying over of the motion.

101

SECTION XIX.

143. The Interchange of Motion at the Discharge of a Qun. — The
physical process involved at the discharge of a gun presents some
points worthy of notice, which we will here allude to. Considering
the state of the case previous to the discharge, it is well, first, to
have a clear conception of the fact of the ether pervading with
the utmost facility the body of the cannon, the ether occupying
the molecular interstices and surrounding the molecules of the
metal, so that, therefore, the slightest difference of the ether
pressure (due to any disturbing cause) would immediately readjust
itself across the body of the gun. It may perhaps facilitate the
conception of this, if the known fact be kept in view that even the
gross molecules of matter (such as the molecules of hydrogen gas)
will permeate and pass through iron at a moderate temperature ;
and the dense metal, gold, is permeable by water under pressure.
So that in addition to the molecular interstices which the ether
pervades freely, the metal must also be porous.

We observe, therefore, before the discharge, the ether enclosing
its intense store of motion pervading the body of the cannon, and
inserting itself between every molecule of gunpowder, ready to
part \\ith a portion of its motion at any instant. The molecules
of gxmpowder are also in an intense state of vibration, due to the
high absolute temperature existing (normal temperature). We
note, therefore, an mgeniously disposed and delicately poised train
of matter, at present in a state of dynamic equilibrium, the whole
pervaded by a physical agent of exhaustless energy, from which it
is only necessary to divert a small portion in order to cause the
propulsion of the shot. The blow struck upon the percussion cap,
by urging a few of the vibrating molecules into proper proximity,
is suiBcient to upset this equilibrium of motion, and brings the
ether into action, the motion passing from the ether through the
train of matter to the shot, and thence to the ether (in the waves
emitted by the incandescent gases, the work of the shot, &c.), in a
cyclical process. As regards the mode in which the process
effects itself, the same considerations apply as in the case already
considered of the explosion of the mixed gases, oxygen and
hydrogen.

During the time of the explosion the ether particles in the
bore of the gun lose a certain fraction of their normal velocity by
transference to the molecules of gunpowder, which loss of motion,
if it continued without renewal, would conduce to a reduction of
the ether pressure in the interior of the gun ; so that the inference
is necessary that on the instant of the disturbance of the equi-
librium of the ether pressure by the motion transferred to the
first few molecules of gunpowder, a readjustment of pressure com-

102

mences to take place across the body of the gun in the fonn of a
wave, the free communication existing with the external ether
rendering it impossible for any appreciable diiBTerence of pressure
to accumulate; and, therefore, during the whole time of the
explosion a continuous wave, representing a succession of small
decrements of velocity sustained by the ether particles (the decre-
ments being very small compared with the normal velocity of the
f-articles), must pass through the gun, the energy of the ether
within tne gun being in this way sustained continuously during
the explosion ; and on account of the high speed of the particles
the loss of motion is, during the comparatively slow process of the
explosion, spread over a vast radial volume of the ether, whereby
local disturbance of the equilibrium of the ether is prevented.
The spherical wave expands as it recedes, distributing the loss of
motion at last over so vast a number of particles, that the loss
of motion, although existing as a whole, soon practically ceases to
exist as far as each particle taken by itself is concerned. It forms
a point of mechanical interest to note the process by which this
motion is renewed, and the lost motion got rid o^ transmitted to a
distance, and dissipated by subdivision ; also to note the neat way
in which the two mechanical conditions fit into each other, viz.
the high speed of the particles of the agent being the only
condition on which the agent can effect an intense development of
work, and at the same time this is the very condition on which
alone the renewal of transferred motion can take place with
adequate speed.

144. The interchange of motion in such a case as this, and,
indeed, in the general phenomena of the interchange of motion
between the ether and the molecules of matter, might properly be
regarded as constituting a " focus of energy." When, for example,
in the present case, the process of the explosion has attained its
maximum, we have a focus of energy, represented by the projected
shot and products of combustion, or we have motion withdrawn
from all sides radially and concentrated at a focus, the loss of
motion by the ether diminishing as the square of the distance
from the focal point Conversely, when the projected products of
combustion at first vibrating up to incandescence, suddenly lose
their motion by retransference to the ether, we have a loss of motion
by matter at a focal point, and an equivalent gain of motion by the
ether, the gain diminishing radially from the focal point; the
collective sum of motion having remained constant at every
instant, before, during, and after the explosion. The gain of
motion at the focus being concentrated at a point of space, is
extremely intense ; and since this motion is that of visible masses,
and of palpable clouds of expanding vapour, this gain of motion
naturally appeals directly to the senses. The equivalent loss of
motion by the ether being subdivided or distributed over a vast
radial volume of the ether, and this loss representing but a very

103

small part of the normal velocity of the particles, this loss of
motion naturally cannot appeal directly to the senses ; indeed, if
the loss of motion could make itself directly palpable to the senses,
then the agent would be incompetent to perform its work properly.

145. If the effect of the explosion of gunpowder be considered,
then it may be said that, as a mechanical means to an end, the
action of the ether is the only conceivable 'process by which the
result could be attained, for the object is to impart suddenly to
small masses of matter (the molecules of gunpowder) a rapid
motion, for the production of a forcible mechanical effect Now,
to impart this rapid motion there must exist a still more rapid
motion at disposal, or, in other words, the component particles of
the motive agent must have a higher velocity than that intended
to be developed, for in order for the particles of the agent to
sustain their action against the small masses (molecules), these
particles must at least have such a velocity as to enable them to
follow up with facility the movements of the small masses. Thus,
for instance, in a precisely analogous way, the motion of the
molecules of gunpowder must be more rapid than the motion of
the shot, or these molecules would be wholly incapable of sustaining
their action against the rapidly advancing shot. So in the same
way the motion of the ether particles must be more rapid than
that of ihe molecules of gunpowder, or these particles would be
wholly unable to sustain their action against the molecules. The
molecules of gunpowder merely serve as the convenient mechanism
to transmit the motion of the ether to the shot, for the gunpowder,
like the shot, has no motion of its own, and, therefore, must have
the motion imparted to it. The ether, on the other hand, does
not require to have motion imparted to it, since it already has
motion. The ether is, therefore, the only competent source of
motion; or the ether transfers motion which it already has
through the gunpowder to the shot, the sum of motion thereby
remaining constant.

146. We have now to consider a few points as regards the
mode of action of the process. Here again the influence of vibra-
ting energy upon the positions of equilibrium of molecules, as
illustrated by the expansion and eventual dissociation of matter
by heat, has an important part to play. The explosion of gunpowder
being simply a case of rapid combustion, precisely the same con-
siderations apply here with reference to the gradual approach of
the components of the compound molecules after combination, sub-
ject to the utilization of the heat, as was treated of in the case of
combustion; and with the additional important practical point
here, viz. that the pressure against the shot is thereby greatly
equalized and the initial strain moderated, or the advance of the
shot along the bore of the gun brings the ether into fresh action.

In order to follow the steps of the process we must consider
certain points. The first act of the ether is to generate the

104

translatory motion of approach of the molecules in the process of
combination. Those molecules which approach each other in the
process of combination to form compound molecules, we shall term
** components." Secondly, this translatory motion of approach of
the components is resolved into a vibratory motion of the com-

Sonents, due to these components in their mutual approach being
riven against the intercepted oscillating ether column in sjm-
chronous vibration. The compound molecules immediately after
combination are therefore vibrating powerfully. This sudden de-
velopment of vibrating energy has, by the stationary vibrations
suddenly set up in the intervening ether, the effect of drivteg
apart in all directions the compound molecules which, after combi-
nation, happen to be in the vicinity of others, a general translatory
motion of compound molecules (the motion of gaseous matter)
being thus set up, by which the molecules are driveli in all direc-
tions with great force agaiust the shot.

147. When two molecules are forcibly urged towards each
other, whereby the molecules are driven against the intercepted
oscillating ether column, the accession of vibrating energy thus
produced acts as a resistance tending to check the approach of the
molecules, or this accession of vibrating energy tends to urge the
molecules farther apart ; so therefore, conversely, an accession of
vibrating energy artificially produced (as by heat) will urge the
molecules farther apart. Thus the vibrating energy (heat) pro-
duced at the approach of molecules in the act of combination
tends to urge the molecules farther apart, and the effect> therefore,
is that the molecules do not approach into such close proximity as
they would do if this accession of vibrating energy were not
developed; and as this vibrating energy (heat; is subsequently
expended, the molecules gradually approach into closer proximity.
Since, therefore, an accession of vibrating energy urges mole-
cules apart, i. e. produces a translatory motion of the molecules
from each other, vibratory motion is thereby convertible into trans-
latory motion ; and since, conversely, a translatory motion of two
molecules towards each other is followed by an accession of their
vibratory motion, translatory motion is thereby convertible into
vibratory motion.

148. The mutual convertibility of these two fundamental forms
of motion admits of further illustration if we take the case of
a metallic bar ; when by producing a motion of translation of the
molecules of the bar towards each other (by compressing the bar),
this translatory motion is converted into vibratory motion (heat) ;
and, conversely, when the vibratory motion of the molecules of the
bar is artificially increased (as by heating the bar), this vibratory
motion is converted into translatory motion, or the molecules are
caused to recede (as observed in the expansion of the bar).

So in the case of the action of the gunpowder under considera-

^jon, the sudden development of vibratory motion in the compound

molecules after combination, causes tTneae mol^xsl^s to recede or

105

rebound from each other in all directions, vibratory motion being
thereby converted into translatory motion ; or the vibrating energy
of the ether column intercepted between each pair of receding
molecules is reduced by an amount representing the translatory
motion imparted to the molecules, and thus the molecules are
chilled at their recession.

149. Translatory motion and vibratory motion are therefore
mutually con/vertible, or the one will produce the other. These
constitute the two fundamental and interconvertible forms of
motion, by the permutations of which all the varied molecular
effects are produced. The mutual convertibility and dependence
of these two fundamental forms of motion constitute, therefore, an
important practical principle in connection with the working of
physical phenomena.

150. Thus, in the physical process involved in the case of
gunpowder, translatory motion is first converted into vibratory
motion, as illustrated by the development of vibratory motion
(heat), due to the translatory motion of approach of the com-
ponents of the molecules under the action of the ether ; and then
this vibratory motion is reconverted into translatory motion^ as
illustrated by the sudden rebound of the intensely vibrating com-
pound molecules after combination. The principle involved in the
process of the explosion is therefore simply that translatory
motion is converted into vibratory motion, ana then reconverted
into translatory motion. These form the necessary mechanical
steps of the simplest conceivable character, by which the trans-
latory motion of approach of the components of the molecules
under the action of the ether is finally resolved into a form of
motion capable of acting against the shot.

151. As regards the order of the steps of the physical process,
the mode of action in the case of gunpowder may serve as a type
of explosives, and of all cases of combustion and of chemical
reactions generally; or in all cases translatory motion is con-
verted into vibratory motion, and then reconverted into translatory
motion ; or to particularize more exactly, the translatory motion of
approach of the components to form compound molecules is con-
verted into a vibratory motion of these components, and this
vibratory motion of the components is finally converted into a
translatory motion of compound molecules.

In some cases of extremely feeble reactions the vibratory
motion (heat) developed may not be sufficient to cause an actual
rebound of compound molecules in the form of vapour, but the
compound molecules may simply recede from each other a short
distance in translatory motion without actually separating. The
amalgamation of zinc may serve as an illustration of such a feeble
chemical process. Here, after translatory motion has been con-
verted into vibratory motion (heat) at the approach of the
component molecules of mercury and zinc to form compound
molecules, these compound molecules \xi^t<bVj x^^^^<^ ^ "^^^

106

distance from each other by the conversion of vibratory motion
into translatory motion (as illustrated by the slight expansion of
the zinc from the heat developed); but the vibratory motion is
here not intense enough to cause a rebound of the compound
molecules in the form of vapour. In the case of the approach of
the molecules of oxygen by the combustion of a piece of mag-
nesium wire, on the other hand, the vibratory motion developed is
such that by its conversion into translatory motion the compound
molecules of the solid magnesia are driven from each other in the
vaporous form.

152. Translatory motion and vibratory motion, therefore, being
interconvertible^ these two forms of motion have necessarily an
intimate dependence upon each other, the slightest increase or
diminution of the one being followed by a corresponding increase
or diminution of the other. Thus, for example, in the illustrative
case of the gunpowder, as the translatory motion of the compound
molecules is being expended by transference to the shot, vibratory
motion (heat) is being continually converted into fresh translatory
motion, or the translatory motion of the compound molecules is
sustained at the expense of their vibratory motion; and this
vibratory motion is itself again sustained at the expense of the
translatory motion of approach of the components of the com-
pound molecules under tne action of the ether, these components
being slowly and forcibly urged into closer proximity by the ether
as the shot advances, thereby developing fresh vibratory motion,
and, by its conversion into translatory motion, giving a fresh im-
pulse to the shot. The advance of the shot along the bore of the
gun, therefore, brings the ether into fresh action, or the demand for
energy causes a fresh supply.

153. As an analogous example of the interconveriibilittf and
mvdiv>al dependence of translatory motion and vibratory motion,
we maytaSe the known fact that, in the case of gases, temperature
and pressure are mutually dependent. The temperature (heat of
the gas), however, consists in the vibratory motion of the mole-
cules which give rise to the observed rapid and periodic ether
waves of heat, the pressure of the gas being produced by the trans-
latory motion of the molecules ; and any disturbance or variation
of one of these forms of motion is attended by a variation of the
other, or the equilibrium of motion readjusts itself by conversion
of the one form of motion into the other. Thus, if an impulse be
given to the translatory motion of the rebounding molecules of a
gas by suddenly compressing it, then the equilibrium of motion
readjusts itself by the conversion of the excess of translatory
motion into vibratory motion (heat), as indicated by the rise of
temperature; and, converselv, if the vibratory motion be artificially
increased (as by exposing the gas to a source of heat waves), then
the excess of vibratory motion is converted into translatory
motion, as indicated by the rise of pressure. The increase in the

velocity of translatoij motion attendant ou the increase of the

107

vibratory motion in heating a gas is also illustrated by the increased
velocity with which the molecules of a heated gas in their mutual
interchange of motion transmit any impulse (such as a wave of
sound).

The interchange of motion between two gaseous molecules
forms an illustration of the permutations of translatory motion and
vibratory motion. Thus, at the approach of the two molecules,
each comes to the end of its path previous to rebounding, by con-
verting its translatory motion into vibratory motion (heat), and,
conversely, the rebound takes place by the conversion of vibratory
motion into translatory motion. The interchange of motion be-
tween a group of molecules forms a perfectly analogous case.
Thus, at the interchange of motion between two billiard-balls, for
example, each ball comes to rest for an instant (previous to re-
bounding) by converting its translatory motion into vibratory
motion (heat); and at the rebound vibratory motion is, con-
versely, converted into translatory motion.

154. The general phenomena of evaporation constitute another
example of the interconvertibility of these two fundamental forms
of motion. Thus, to take the important practical case of the
generation of steam, for instance. Here, by the transmission of
vibratory motion from the molecules of fuel to the molecules of
water, the rebound of these water molecules in free translatory
motion (in the form of steam), takes place by the conversion of
their vibratory motion (heat) into translatory motion.

An endless variety of examples might be referred to, as illustra-
tive of the important part these two i^damental forms of motion
have to play in the working of physical phenomena ; indeed, from
the very fact that all molecules on the earth's surface possess an
extreme intensity of vibratory motion, and since translatory
motion constitutes the one conceivable permutation of which
vibratory motion admits, and since also all physical processes in
their fundamental working depend on translatoiy movements of
approach and recession, in which these two forms of motion are
directly concerned, there is, therefore, perhaps scarcely a move-
ment of matter in which the interconvertibility of these two
fundamental forms of motion has not a part to play.

SECTION XX.

155. The mode in which the supply of energy by the ether is
influenced by the demand constitutes a noteworthy point; and to
illustrate this somewhat further, we may trace the steps of the
process backwards in the previous illustrative case of the gun-
powder, this serving as a type of molecular actions. If we regard
the gaseous molecules impinging against the advancing shot within
the bore of the gun, and selecting any o\i<^ T£i<c\!^\i\!^^ ^^q^\^ "^c^^s^

108

molecule, in being driven against the shot, must have rebounded
from some other molecule in the rear. The intercepted pulsating
ether column, therefore, which caused the mutual rebound of the
two molecules (thereby propelling the molecule against the shot),
accordingly lost by transference an amount of vibrating energy
equivalent to the work done ; or, in other words, at the rebound
of the two gaseous molecules, both the intercepted ether column
and the molecules themselves lost vibratory motion by its con-
version into translatory motion. This loss of vibratory motion by
each compound gaseous molecule, however, disturbs the equili-
brium of the ether pressure between its vibrating components.
The ether accordingly comes into action, readjusting the equili-
brium of pressure by urging the components into closer proximity,
thereby developing fresh vibrating energy, and by its conversion
into translatory motion giving a fresh impulse to the shot ; and
thus the advance of the shot along the bore of the gun by this
special physical process brings the ether into fresh action, or the
demand for energy entailed by the advance of the shot causes a
fresh supply. It forms a beautiful mechanical process to con-
template the expanding gas as the shot advances, followed by the
closer approach of the components of the compound molecules under
the action of the intense ether pressure, the attendant partial
renewal of vibrating energy, and its instant conversion into trans-
latory motion, whereby the action directed against the shot is
renewed, the ether following up the eflFort in a beautiful manner,
and adjusting the supply of energy in accordance with the require-
ments of the work. By this special physical process, therefore,
not only is the initial production of heat moderated, and the
development of heat equalized by being spread over a certain
interval of time ; but what is more important, the initial strain
upon the gun is moderated, and instead of the intense initial heat
and strain that would result were all the energy expended by the
ether concentrated in the first instant of the explosion, the energy
of the ether is held to a certain extent in reserve, and part is given
oflF after the shot has had time to get in motion, the strain against
the gun being thus equalized, and the effort directed against the
shot thereby finely graduated by being spread over a certain
interval of time.

156. If we imagine a case where gunpowder is exploded in a
perfectly closed vessel, strong enough to bear the pressure without
yielding, then here no means whatever are given for the perform-
ance of work beyond the slow communication of vibratory motion
(heat) to the molecules forming the sides of the vessel, so that,
therefore, the action of the ether would be checked, or its energy
would be held in reserve. The components in the process of com-
bination would be merely driven in a short distance towards each
other, their farther approach being checked by the absence of
means tor utilizing their vibratory motion. If we imagine the

109

vessel to burst while this high temperature still exists, then
the sudden facility thus given for the performance of work
would bring the ether into fresh action; for vibratory motion
being then rapidly converted into translatory motion in the
free expansion of the gas, the ether would therefore soon urge
the components of the compound molecules into their final
positions of proximity. If we suppose the vessel to hold until
the enclosed gas assumes the normal temperature, then the
slow communication of vibratory motion to the molecules forming
the sides of the vessel would keep the ether in action during the
whole time of the cooling down, the components of the confound
molecules being slowly and forcibly urged into closer proximity
as their vibratory motion is given off; fresh increments of vibratory
motion and fresh increments of translatory motion being thus con-
tinually developed as the cooling down proceeds. The result would,
therefore, be that the temperature of the enclosed gas would fall
more slowly than if the above action did not take place.

157. Conversely, when gunpowder is exploded in a perfectly
unconfined state, the work of the ether is done much quicker or
in less time, for here means are given for the performance of work
in the expansion of the gas, and vibratory motion being thereby
rapidly converted into translatory motion ; the ether accordingly
rapidly follows up the demand for energy by urging the com-
ponents of the compound molecules into closer proximity, these
components soon approaching into their final positions of equi-
librium due to normal vibrating energy, where the work of the
ether ceases.

SECTION XXI.

158. The Physical Conditions which determine Combustion, —
In proceeding to consider briefly the physical conditions upon
which the development of the phenomena of combustion, &c.,
depends, we may note, first, the fact previously referred to, that
heat (i. e. an elevation of temperature above the normal) is in
general unfavourable to a stable state of chemical union ; or heat,
as a general rule, tends to separate chemically combined mole-
cules, and indeed at a certain elevation of temperature (tempera-
ture of dissociation) chemical combination is entirely prevented.
Heat, therefore, can by no means be said to be in itself the
essential condition to develop combustion.

The condition required to produce combustion may be simply
stated to be, that the molecules concerned should be brought into
a certain degree of proximity; to eflfect which result a certain
amount of force is in general required.

110

Now, in most cases the most conyenient way of bringing the
molecules concerned into the requisite proximity is by producing
a forcible molecular disturbance by some cause for which heat
(L e. matter in intense molecular vibration) is well adapted ; so
that this may serre to explain why in most cases in practice heat
is applied in the first instance to develop combustion, and after
combustion has once been developed, the continuous molecular
disturbance thus kept up, by continually urging additional mole-
cules into the requisite proximity, has the effect of maintaining
combustion, so that combustion becomes, as it were, a self-acting
process.

159. Thus, for example, when a jet of gas is turned on, the
molecules of air and gas are interchanging motion among each
other in the free translatory motion characteristic of the gaseous
state ; but this normal rate of translatory motion is not sufficient
to carry the molecules over the outer neutral point in their
mutual interchange of motion. By the application of a flame
(vibrating matter), vibratory motion is imparted to the molecules
of air and gas, and this vibratory motion being converted into
translatory motion, combustion accordingly sets in as soon as the
molecules have by increase of their translatory motion acquired a
sufficient momentum to carry them over the outer neutral point
in their mutual interchange of motion ; and after combustion has
once set in, the flame, by continually developing translatory
motion in the adjacent molecules of air and gas, thereby serves
the purpose of giving that small initial impulse which is requisite
to bring the ether into action in chemical combination. The
special action of heat in developing and maintaining combustion
would therefore simply consist in giving such a degree of trans-
latory motion to the molecules concerned that they are carried
over the neutral point in their mutual interchange of motion.

By the combustion of a solid body, the same considerations
would hold as in the case of a gas, in so far as it is known that in
the case of a solid body in the proC/Css of combustion, the mole-
cules of the solid are in great part carried up in the form of
vapour before combustion ensues; although the inference is
necessary that combustion might go on at the surface of a solid,
provided the translatory motion of the impinging air molecules
was augmented to a sufficient degree by the presence of the
flame.

160. If by any means two molecules could be brought up to
the outer neutral point (i. e. that point where the ether in the
process of combination first comes into action) slowly, so that the
vibrating energy generated in reaching this point had time to
dissipate itseK, so tnat, therefore, the two molecules arrived at the
outer neutral point still at normal temperature, then this physical
condition would be eminently favourable to the energetic com-

bination of the molecules, the ether coming into action with

Ill

angmented energy, owing to the absence of a previous abnormal
increase in the vibrating energy of the molecules.

We do not mean to assume that the quantity of heat gene-
rated at the combination of molecules at normal temperatures is
greater than the quantity generated at the combination of the
molecules after having been previously heated, for the process of
combination in the case of heated molecules is necessarily spread
over a longer period of time, so that the total quantity of heat
generated may well be appreciably the same as in the case of
molecules at normal temperature whose combination takes place
with greater energy and lasts a less time. In the case of mole-
cules at normal temperature, the velocity of translation generated
by the ether is necessarily greater, or the ether comes into action
with greater energy, the molecules, therefore, being in the first
instance driven in nearer to each other than in the case of mole-
cules previously heated ; but in both cases, i. e. whether the
molecules have been previously heated or not, the final positions
of equilibrium taken up bv the molecules are the same as regards
relative distance, when the temperature, after combination, has
fallen to the normal, the relative distance of the molecules being
determined solely by vibrating energy.

The physical means of bringing molecules thus into the requi-
site proximity for combination (combustion) to ensue, without
previously heating the molecules, would evidently be the ap-
plication of an intense but gradually applied pressure to the
molecules concerned.

161. However, we may observe that in that case, where
either one or both of the reagents employed are a gas, certain con-
siderations would indicate that it would be impossible to produce
combustion without initial heat, and this would therefore apply to
the general cases of combustion, where the atmosphere is one of
the reagents. This would follow from the consideration that the
molecules of a gas are in free translatory motion, and are there-
fore quite beyond control, so that the application of a pressure
would be of no avail in this case; for evidently the only possible
means of causing a gaseous molecule in free translatory motion
to approach nearer to the combustible from which it rebounds, is
by augmenting the translatory motion of the molecule. The de-
gree of proximity into which a gaseous molecule approaches to
the surface molecules of the combustible by whose vibrations set
up in the ether the approach of the gaseous molecule is at first
checked, will clearly depend on the velocitv of translatory motion
of the molecule, and it therefore follows that since the molecule
is beyond control, the only possible means to make it approach
into suflBcient proximity for combustion to ensue is by augmenting
the velocity of approach of the molecule, whereby its momentum
may be sufficient to carry it over the outer neutral point. Since,
however, it is a physical impossibility to change the rate of transr

112

latory motion of a gaseous molecule without heating it, or an
impulse cannot be given to the molecule without increasing its
vibratory motion, it follows, therefore, that combustion cannot be
developed, when a gas is one of the reagents employed, without
initial heat. Thus, it would probably be impossiole to explode
a mixture of oxygen and hydrogen gases by a gradually applied
pressure, however intense, at least so long as the gaseous state
was retained ; for the increase of pressure (slowly applied) would
only have the effect of bringing a greater number of molecules
into the unit volume of space, or of reducing the mean length
of path of the molecules; but so long as the temperature, and
therefore the rate of translatory motion of the molecules, re-
mained constant, the molecules in their mutual exchange of
motion would not approach into greater proximity than if the
pressure had not been applied ; so that the inference follows that
so long as the gaseous state is retained, no amount of pressure
would develop combustion. This consideration applied to the
atmosphere (matter in the gaseous state), the principal reagent
in combustion, would indicate the existence of a special condi-
tion for safety.

On the other hand, in that case where both the reagents are
in the solid state, and therefore the molecules are completely
under control, having stable positions of equilibrium, then there
is no reason to doubt that combustion might be produced by the
application of a pressure suflSciently intense to bring the mole-
cules into the requisite proximity. Thus, probably percussion
powder might be exploded by a graduaEy applied but intense
pressure, and the inference appears warranted tnat the explosion
in such a case would be exceptionally violent, since all the mole-
cules of the mass would be brought at about the same time into
proper proximity, resulting in the simultaneous combination of
the entire mass, the ether also coming into action with aug-
mented energy, due to the favourable temperature of the mole-
cules, or the absence of a previous abnormal increase of their
vibrating energy.

162. Regarding the immunity of gases from combustion by
pressure, or the impossibility of combustion being developed by
pressure alone when one or both the reagents are a gas, there
are certain possible exceptional conditions which we may here
notice as possibly having a practical interest. It is a known fact
that the molecules of gases adhere to the surface of solids in the
form of a thin film, the gaseous molecules in this condition being
fixed as if they were the molecules of a solid body. Hence, in
this case, if the substance were combustible, the deduction is war-
ranted that a combination of the molecules might be effected by
a gradual and suflSciently intense pressure applied to the mole-
cules of the film, the gaseous molecules in this case being quite
under control, or they may be rearlily pressed against the com-

113

bustible to which they adhere. Porous bodies, which expose a
large surface to the atmosphere, stored in considerable quantities
so as to be under pressure, would be the physical conditions most
favourable to produce the above result. We cannot avoid the
conclusion that the phenomena popularly termed phenomena of
" spontaneous combustion " are simply physical examples of com-
bustion by pressure under these conditions. To select a well-
known example, if we take the case of a stack of hay ; then this
material is full of pores, which are penetrated by the air, a film of
air adhering to the interior of each pore, the whole forming a very
extensive area: the molecules composing the film having lost
their free translatory motion resemble the molecules of a solid
body. The only condition required, therefore, would be a suflScient
pressure to urge a few of these molecules of air into such
proximity with the combustible material (carbon molecules, &c.) of
the stack, that the neutral point is reached when the ether coming
into action, the stack might thus be set on fire or charred in
places, as in accordance with observation, assuming that the
weight of the superincumbent material was suflScient to satisfy
the condition for pressure. In an analogous manner, the develop-
ment of combustion in coal, when stored in considerable quantities
so as to be under pressure (and possibly partly in a finely-divided
state), may aflford another example of combustion due to the above
physical causes. The occurrence of a like effect in the case of
stored oiled cotton and other substances distinguished for their
porosity, may be cited as possibly constituting other examples of
the development of combustion under the above special physical
conditions.

SECTION XXIl.

1G3. Absolute Quantity of Energy in the Unit Volume of Space.
— We shall now consider more particularly the energy enclosed
by the ether, with the endeavour to give some idea of the absolute
value of the energy represented by the motion of the ether par-
ticles contained within a given portion of space, with the object, if
possible, to fix upon a limiting value for this energy, or the lowest
value consistent with what physical facts would require.

The conditions required in order to determine the amount of
energy enclosed in the unit voltime of space are clearly, first, a
knowledge of the quantity of matter in the form of ether con-
tained in the unit volume of space (i. e. the density of the ether) ;
and secondly, the normal velocity of the ether particles. Now,
although we do not know the density of the ether independently,
nevertheless since density is determined by pressure and velocity

114

of component particles, if, therefore, by a known limiting value
for the velocity of the ether particles, a limiting value for the
ether pressure can also be fixed upon, then a limiting value for
the etner density is thereby given. The limiting value for the
velocity of the ether particles is given by the measured velocity
of a wave of light. As regards the value for pressure, we take the
estimate already fixed upon : that this amounts to 500 tons per
square inch £ts the lowest limiting value. There are valid grounds
for inferring that this value for pressure has been under-estimated ;
for we assumed the total ether pressure as a small multiple of the
observed difference of pressure in the case of " cohesion," whereas,
as before remarked, it is a known fact that the force required to
separate chemically combined molecules must be many times
greater, this indicating the high intensity of the controlling ether
pressure, and showing that an estimate of this pressure from the
case of *' cohesion " must, be but an inadequate representation of
the reality. The tremendous energy developed in explosives,
which is tlie very energy of the ether itself, is a direct indication
of the intensity of tne ether pressure, which is the necessary
accompaniment of this energy.

That this value for pressure has been under-estimated, a bare
consideration of the dependent value for density would almost
show, for the ether density corresponding to this pressure
( aaglflOQ of the atmospheric density) represents a density so
insignificant as to be less than that of the best gaseous vacua.

164. The actual density of the ether might, therefore, well be
greater than the above estimate. A greater density would, of
course, involve a proportionally greater pressure. It is, however,
well to keep in view that there is not the slightest mechanical
impediment to the existence of an extremely intense pressure, for
so long as the pressure about a molecule of matter is under
normal conditions perfectly balanced, it can be of no special
import what its value is. If, for example, it were an essential
condition to a steady and perfectly balanced pressure that the
density of the ether, i. e. the quantity of matter relatively to the
volume of space, should be infinitesimal, then the observed steadi-
ness of the stable aggregation of molecules determined by the
ether pressure would warrant the inference that such was the fact.
But the actual physical conditions are quite otherwise; for an
addition to the quantity of matter contained in the unit volume of
space, or an addition to the number of ether particles, so far from
rendering the pressure due to the motion of these particles less
steady, would only render it more steady ; and thus, although by
this increase in the number of particles (increase of density) the
pressure might be greatly increased, the concealment of the exist-
ence of the pressure from the senses would, on account of the
perfection of the equilibrium, be if possible more eflectual ; and
although the value of the energy enclosed might thus be greatly

115

augmented, the reduced length of path of the particles would only
serve to remove the motion still farther beyond the reach of
detection by the senses. Hence we may observe the perfect
mechanical possibility of the existence of an ether density very
much greater than the above estimate. We will, however, take
the above estimate for the ether density as a basis for deducing
the value of the enclosed energy, it being only our object to arrive
at a limiting value for this energy, having therefore valid grounds
for concluding that the results arrived at for the value of this
energy will be less than the facts as they actually exist.

165. To give an idea, first, of the enormous intensity of the
store of energy attainable by means of that extensive state of
subdivision of matter which renders a high normal speed practi-
cable, it may be computed that a quantity of matter representing
a total mass of only one grain, and possessing the normal velocity
of the ether particles (that of a wave of light), encloses a store of
energy represented by upwaids of one thousand millions of foot-
tons, or the mass of one single grain contains an energy not less
than that possessed by a mass of forty thousand tons, moving at
the speed of a cannon ball (1200 feet per second); or other-
wise, a quantity of matter representing a mass of one grain
endued with the velocity of the ether particles, encloses an amount
of energy which, if entirely utilized, would be competent to
project a weight of one hundred thousand tons to a height of
nearly two miles (1*9 miles).

This remarkable result may serve to illustrate well the intense
mechanical eflfect derivable from small quantities of matter
possessing a high normal velocity, the extremely high value of the
effect depending on the fact that energy rises in the rapid ratio
of the square of the speed.

166. A cubic foot of air weighs 56*5 grains, so that with the
above limiting value for the ether density (s ^bI&o o that of air), a
quantity of ether representing the total mass of one grain would
be contained in a cubical portion of space with side of cube equal
to about forty-five feet. Hence a portion of space of these
moderate limits contains, in the energy of the concealed motion
of the enclosed ether, not less than the above prodigious work-
producing power.

167. With the above limiting values for normal velocity of
particles and density, we may give a few more numerical results
illustrative of the energy enclosed by this great physical agent.
The energy in the form of concealed motion contained in one
cubic foot of space amounts in units of work to not less than
ten thousand seven hundred foot-tons. This is the energy which
a projectile of one quarter of a ton would possess when moving at
the rate of 1600 feet per second. Since this velocity happens to
be that of the molecules of air in their translatory motion at
noimal temperature, it may be of interest to note that the e\\ftx^

116

enclosed by a cubic foot of ether represents the energy of trans-
latory motion of the molecules (not taking into account the vibra-
tions of the molecules) of a quarter of a ton of air. This amount
of air would occupy a cubical space with side of cube equal to
about forty-one feet, and the energy of the translatory motion of
the molecules of this mass of air would be competent to project
it to a height of about seven miles.

168. That which appeals most directly to the senses as energy,
and which our ideas naturally connect with the visible motions of
large masses of matter, is but insignificant when compared with
the energy of the concealed motions of molecules, and is as
nothing when compared with the intensity of the energy enclosed
by the ether in the motion of its particles.

It is our object to consider this question in all its points, for
we do not content ourselves merely with putting forward the bare
deduction, to which we have been necessarily led, that this
energy exists; but it is our endeavour rather to show the con-
sistency of the fact ; or we examine all the points of the
physical problem with the view to show that the existence of
this intense energy on all sides as a physical fact admits of
being brought into harmony with just mechanical principles, and
of being practically realized and appreciated.

On the first consideration of the subject there may undoubtedly
be a diflSculty in forming a satisfactory conception of the existence
of an agent enclosing such an intensity of energy as this ; indeed,
at the first thought there may even appear something wild in the
idea of the continued presence of an agent competent to transfer
motion to explosives; indeed, one would perhaps naturally ask,
How can such an intensity of energy exist without making itself
directly palpable to the senses in the normal state of the ether ?
The answer to this is, that it is theoretically deducible beforehand
that the existence of such an intense store of energy is perfectly
consistent with its concealment from the senses ; indeed, that so
far from concealment being inconsistent with its existence, it may
be shown (on grounds already pointed out) that concealment is
absolutely essential to its existence; in fact, that without con-
sidering the question as to its existence at all, it is theoretically
deducible beforehand as an independent deduction that if sucn
an intense store of motion did exist, then it would necessarily be
concealed ; and further, that the existence of a store of motion of a
high intensity is the necessary consequence of the known impalpdhle
quality of the ether ; the agent becoming less and less palpable to
the senses as the rapidity of the motion of its component particles
increases ; and therefore the less palpable the agent, or tne more
effectual the concealment of the motion from the senses, the higher
would one be warranted, on theoretic grounds, in assuming the
J22 tensity of the enclosed store of energy to be.

169. It is well te keep the above considerations in view, since

117

there is an undoubted tendency to ignore the existence of any-
thing which does not appeal directly to the senses. If such a
course were followed, however, a vast number of important
physical facts would pass unknown, and work their influences
unheeded, for the most important facts may not always lie on the
surface. Thus, if we take the important phenomena of Heat, for
example. The motion termed "Heat" is, under normal conditions,
completely concealed, and how intense (as expressed in mechanical
units) is the energy of the molecular motion of substances at
normal temperature this energy greatly surpassing the energy
of the movements of large masses which appeal to the senses.
If, therefore, the existence of this concealed energy be admitted
and realized, then there can be no real diflSculty in appre-
ciating and harmonizing with just mechanical principles the
enclosed energy of the ether; for if the gross molecules of
matter attain such an intensity of motion as the mechanical
equivalent of heat proves, then how much more may the minute
component particles of the ether, whose motion is entirely un-
obstructed, attain a high normal speed ? And when the existence
of the rapid motion is once appreciated, then the existence of
' the intense store of energy follows as an absolutely necessary
consequence.

170. The normal speed as deduced for an ether particle may
naturally appear inordinately high, according to our general ideas
of speed, which attach themselves to the motions of visible masses ;
but it is well to note that these motions of visible masses take
place under physical conditions which are eminently unfavourable
to the development of high speeds, whereas the concealed motions
of molecules and particles take place under conditions eminently
favourable to high speeds, so that the two cases are not fairly
comparable.

Thus the movements of visible masses of matter near the
earth's surface, where the motions come under the observation,
cannot take place without continual and forcible obstruction by
other matter (the air, &c.), so that the attainable speeds are very
limited in such a case, and yet this is precisely the case from
which our general ideas of speed and energy are formed. The
motion of the molecule of matter, .on the other hand, can take
place with comparative freedom, the ether being the only obstruc-
tion, and the resistance thus oflered is but small. Hence we may
observe that the motions of molecules take place with some
rapidity, as illustrated, for example, by the rapid translatory
motion of thfe molecules of gases, which by their interchange of
motion can propagate waves at a considerable speed.

The motion of the ether particle, on the other hand, takes
place under the most favourable conditions conceivable, for there
IS nothing whatever to obstruct or curb its free motion. Hence
the possession of a high speed by the ether particles can be said to

118

be only consistent with the special physical conditions of the case.
Even large visible masses of matter may attain high speeds when
the physical conditions are favourable. Thus, in the free ether,
masses of matter are known to attain speeds by which many miles
are traversed even in a second of time, and quantities of matter in
the form of comets are actually observed to be propelled round
the sun at a speed of upwards oi 300 miles per second. If, there-
fore, it be realized that large masses of matter, whose motion must
be obstructed to a certain extent by the presence of the ether,
attain speeds represented by hundreds of miles per second, what
diflSculty can there be in realizing the existence of a high speed
in the case of the minute ether particle, which moves entirely
without obstruction, and whose minute mass renders perfectly
practicable a high speed without producing physical disturbance
of the equilibrium of the molecules of matter which the ether
surrounds ?

Moreover, when it is considered that this motion of the ether
particles constitutes the sole physical means whereby motion can
be transmitted across the vast intervening distances of stellar
space, and that even as the fact stands this transmission of motion
by interchange of motion among the ether particles requires
upwards of three years to traverse the intervening ether which
separates the nearest star; then the above value for the normal
velocity of the ether particles is surely no more than consistent
with the special functions which belong to this great physical
agent.

If, then, the above value for the normal velocity of the ether
particles be realized as a reasonable and consistent fact, then the
existence of the intense store of energy — of the value of which we
have endeavoured to give some idea by a comparison with the
greatest observed cases of energy which appeal to the senses —
follows as a necessary consequence, as certain as the mathematical
fact that energy rises as the square of the speed.

We may just add here that a consideration of the physical
conditions involved in the case given of a comet, may serve as
another illustration of the mechanical fitness of the high normal
velocity possessed by the ether particles, these particles having
such a suitable speed that they are not only able to follow up the
matter forming the comet (travelling at 300 miles per second)
with facility, but are capable of transmitting motion to it, i. e. of
propelling the comet along its course.

171. Since the visible motions of large masses upon the earth's
surface constitute the only means by which a distinct figure or
illustration of energy can be presented to the mind, although
energy in this form can never attain a High intensity, we will take
a few more illustrative cases, as serving to exemplify the far
higher intensity of the energy of concealed motion.

It 18 well to keep practically in view that if it were attempted

119

beforehand to devise what physical conditions should be satisfied
to render possible the existence of a store of energy of the
highest possible intensity, capable of producing dynamic efiects
of the most forcible character, then the conditions satisfied in the
physical constitution of the ether would be precisely those re-
quired. Hence, in dealing with the value of the energy enclosed
by the ether, it is to be expected beforehand that tne results
arrived at will represent extremely high figures as expressed in
mechanical units.

172. If we take the case of a railway train whose weight
amounts to 200 tons, moving at the rate of 60 miles an hour, then
the energy contained in the train is such, that if the motion of the
train were supposed diverted vertically upwards at any instant,
the train would project itself to a height of 121 feet ; or the work-
producing power of the train is therefore 121 x 200 = 24,000
foot-tons. This, however, would only represent the energy of the
concealed motion of the ether contained in about 2^ cubic feet of
space.

If we suppose a collision of the train to take place, then the
energy transferred to matter at the collision, the shock of which
would be precisely equivalent to that produced by a fall of the
train through 121 feet, would only represent the energy which
2^ cubic feet of ether are competent to transfer to matter ; or, in
other words, the transference to matter of the concealed motion of
the ether occupying a portion of space of these moderate limits
would involve a dynamic eflFect greater than that developed at the
collision of a train of 200 tons at the above speed, this point being
illustrated by the destructive eflfects of the transferred motion
of the ether in the case of ** explosives," the dynamic eflfect of
" lightning," &c.

173. To take a further illustration : if we imagine the ether
occupying a cubic foot of space to be replaced by a cubic foot of
lead, or the ether occupying any unit volume of space to be
replaced by lead, then from the known density of the metal, lead,
and from the known fact that energy is in the ratio of the density
or mass, and as the square of the speed, it may be computed that
for the energy contained in this unit volume of space to remain as
before, it would be necessary for the mass of lead to have a trans-
latory motion at the rate of 1470 feet per second (about the
speed of a cannon ball) ; or, in other words, therefore, if space
were filled with flving projectiles which graze each other in their
close proximity, the energy thus existing would be scarcely com-
petent to represent the energy of the concealed motion actually
existing in the normal state of the ether.

The speed attainable by gross masses of matter, such as pro-
jectiles in the atmosphere, is necessarily extremely limited; yet
because this is about the highest form of motion that appeals to
the senses, the motion is naturally considered extremely rapid ;

120

yet it may be shown that the motion of a projectQe vanishes when
compared with the speed of the concealed motion of the ether
particle. Taking the ordinary speed of a projectile, such as a
rifle bullet, for example, at 1200 feet per second, then the speed
of the ether particle (that of a wave of light) is to the speed of the
bullet as 836,000 is to 1 ; or it may be computed that the speed of
the ether particle bears the same proportion to that of the bullet,
as the speed of the bullet bears to the rate of movement of the
extremity of the large hand of a clock 10 inches in length. Since
the motion of such a clock-hand is scarcely perceptible at a few
feet distance, its rate of motion may be justly said to vanish com-
pared with the speed of a bullet ; in the same way, therefore, the
motion of a bullet may be justly said to vanish when compared
with the speed of an ether particle.

SECTION XXIII.

174. Mass of the Ether.— li is an unquestionable fact that the
density of the ether, or the quantity (volume) of matter in the
form of ether, relatively to the unit volume of space is very small ;
nevertheless, considering that the absolute quantity or total mass
of the ether which occupies a spherical portion of space increases
in the extremely rapid ratio of the cube of the radius, it is plain
that the absolute or total mass of the ether may become very
considerable, even when a moderate portion of space is considered.

Taking the above extremely low limit for the ether density
( gggls TRT that of air), it may be computed that the quantity of
matter in the form of ether enclosed within a cubical portion of
space, with side of cube equal to about two miles (2*149 miles),
would represent a total mass of one ton.

175. If we consider the ether contained within the bounds of
the solar system, then it may be shown that by the above remark-
ably low density, the total quantity of matter in the form of ether
enclosed within a radius extending to the limits of the solar
system considerably exceeds the total quantity of matter repre-
sented by the entire mass of the sun, and that of all cosmical
bodies within the system.

Taking the earth's mean density at 5*5 compared with that of
water, the sun's mean density is represented by the number 1 * 364.
The density of the air compared with water is known (weight of a
cubic foot of air being 56*5 grains). Hence, taking the above
value for ether density, given in terms of air, and expressing it in
terms of the sun's density, we obtain the fraction g&gogoooooo *
The 8un^8 radius is known to amount to about four hundred and

.121

twenty-seven thousand miles ; hence, if we take a radius from the
sun's centre, whose length exceeds the radius of the sun in the
same proportion as the cube root of the number of times the sun's
density exceeds that of the ether, we obtain the radial limits in
miles of a spherical portion of space, the total mass or quantity of
matter in the form of ether enclosed within which equals the
total mass of the sun; or we have 427,000 X ^55,606,000,000 =
1,629,800,000 miles.

176. Hence it would follow from this that with the above
limiting value for the ether density, a radius lying somewhat
within the orbit of Uranus (dist. of Uranus = 1,753,000,000 miles)
encloses a quantity of matter in the form of ether, the total mass
of which equals the total mass of the sun.

In the same way it may be computed that the total mass of
the ether enclosed within the orbit of Neptune, representing the
bounds of the solar system, exceeds by more than four times
the total mass of the sun, together with the collective masses of
the planetary members of the system.

In view of these considerations, it might truly be said that
there exists more matter in what is not unfrequently looked upon
as mere space, than the sum total of all that which is distinctively
termed " matter " put together. So far from space being empty,
space is so pervaded by matter, that the particles of matter,
although extremely minute, are in incomparably closer proximity
than the component molecules of solid masses.

177. As the total mass or quantity of matter in the form of
ether enclosed within the limits of the solar system thus con-
siderably exceeds the total collective masses of the sun and the
planetary members of the system, and taking into account the
intensity of the energy enclosed by the ether, it is plain that
the total quantity of energy contained in the sun, represented by
the heat there developed, must 4^0 but insignificant in comparison
with the total energy in the form of concealed motion contained
in that portion of the ether which is confined within the spherical
limits of the solar system ; for since a given quantity of ether
encloses an amount of energy competent to impart to an equal
quantity of matter the normal velocity of the ether particles, it
would follow that a quantity of ether, representing only about one
fourth of that which is contained within the limits of the solar
system, would be competent, if its enclosed energy were entirely
utilized, to impart to the entire mass of the sun the velocity of
light.

178. If, therefore, when only the limited range of the solar
system is regarderl, the ether enclosed within these bounds
represents a quantity of matter exceeding the total mass of the
sun and that of the collective members of the system, and a
quantity of energy far exceeding the total energy developed in
the sun, what must be the fact if we regard the visible stellar

122

nniverse, or that portion of the universe, of the scale and relative
proportions of which a judgment can be formed, and of which our
Sim forms a component stellar member ? Then, as a known fact,
the amount of space occupied by the collective stellar members of
this universe almost vanishes when compared with the amount of
intervening space occupied by the ether, i. e. by the ether which
is confined within the limits of this universe. The dimensions of
the spherical portion of ether, enclosed within the radial limits of
the solar system, would almost dwindle to a point when viewed
from the nearest star.

The considerations applied to our own sun find equally their
application in the case of other stellar suns ; and thus a quantity of
ether surrounding each stellar sun, the radial extent of which
mass of ether almost vanishes when compared with the quantity
of ether pervading the separating distance of this stellar sun from
others, would represent a quantity of matter equal in mass to the
stellar sun, and a quantity of energy, compared with which the
total energy in the form of heat contained in the stellar sun is but
insignificant in proportion.

In view of these considerations, one of the fundamental purposes
of the intense store of energy enclosed by the ether becomes
apparent, the vast total of energy developed in these stellar suns
having been derived from the ether, as it is returned to the ether
as these stellar suns pour their heat into space. When these
points are taken into account, what would otherwise be the
anomaly of the ether receiving all this energy and giving no
return, or the anomaly of these myriads of stellar suns all pouring
their stores of energy imrequited into space, finds its explanation ;
the process actually going on consisting in the return to the ether
of the energy derived from the ether, the process consisting in the
natural return of the energy to its origmal source, to be again
available for useful ends.

SECTION XXIV.

179. There are certain known facts which would tend to the
conclusion that the action of the ether in gravitation was the main

Ehysical cause concerned in the original development of the sun's
eat. If we take the case of a quantity of matter converging
towards a common centre at a high speed, under the feeble but
long-continued propulsive action of the ether in ** gravitation,"
then at the collision of this matter the stationary vibration of the
intercepted ether would be necessarily largely intensified, due to
tlie bigh speed of approach of the molecules; the latter, which are

123

in synchronous vibration with the ether, thereby receiving a
sudden large accession of vibrating energy (heat), and then
rebounding in translatory motion.

If we single out any pair of the approaching molecules, then
it may be observed, that however feeble the initial vibratory mo-
tion might be immediately previous to the collision, this vibratory
motion would be at once reacted upon and raised to a high inten-
sity, due to the rapid shortening and forcible compression of the
oscillating ether column by the rapid approach of the two mole-
cules against which the column abuts, the intense oscillations
of the column then driving the molecules backwards with an
energy which is the greater, the greater the rapidity of their
approach, and vibratory motion is thus converted after the normal
method into translatory motion. The component molecules of
the entire mass of matter would thus, after the approach, rebound
from each other in the free translatory motion of the gaseous
state.

180. In regard to the mode of action in the development of
vibratory motion, there are certain points worthy of notice.
Firstly, the increments of motion given to the oscillating ether
column by the approaching molecules would tend to rarefy the
column, and drive it out circumferentially ; but this is resisted by
the intense ether pressure, so that the oscillating mass of ether is
forcibly curbed between the opposed vibrating molecules, and
thereby its vibratory motion has to bear the full brunt of the
collision, the intensification of the vibratory motion of the elastic
coluDin being greater, the greater the velocity of approach of the
molecules ; and from this latter fact it may be inferred that, how-
ever great the velocity of approach might be, the molecules
could never come into contact.

This point may be illustrated if we suppose an elastic sphere
to be rebounding between two parallel surfaces at a slow rate :
then if it be attempted to make the surfaces approach quickly by
using great force, the impulses given to the sphere would be such
that it would be a complete impossibility to bring the surfaces to-
gether, and the greater the force used, the greater is the resistance
encountered ; and however great the energy of the impulse given
to the surfaces to make them approach, it would only cause the
sphere to rebound with greater energy, the force used defeating
itself. The same point might even be roughly illustrated by
attempting to bring down the hand suddenly upon an indiarubber
ball which rebounds between a horizontal surface and the hand,
when the greater the energy used the greater will be the energy
with which the ball repels the attempt to shorten its path. The
same considerations apply to any intercepted oscillating mass of
matter whatever, as to the previous case of the oscillating mass
of ether between two opposed vibrating molecules in the act of
rapid approach. It is important to observe that by the approach

124

of the opposed vibrating molecules, not only are the pulsations
of the intercepted ether column intensified on account of the
velocity of approach itself, but also on account of the rapid
shortening of the intercepted column attendant on the approach
of the molecules, the number of the successive reflections of the
impulses backwards and forwards between the opposed molecules
increases rapidly as the molecules approach ; and since a fresh
impulse is received at each successive reflection, the vibrating
energy of the column therefore rises in a rapid ratio as the mole-
cules come into proximity.

181. It would be difficult, perhaps, to form a just idea of the
intensity of the vibrating energy that must be developed by the
collision of matter at cosmical speeds, which are so beyond com-
parison with any terrestrial velocities. One of the finest illustra-
tions of the effect produced by these high speeds is afforded by
the passage of those masses of matter termed " meteors " through
the earth's atmosphere, when the molecules of air at their succes-
sive collisions rebound with an accession of vibrating energy
equal to that of flame, and the mass itself is dissipated in vapour.

182. In the case of matter coming together at a high speed
under the long-continued action of gravity, the same considera-
tions apply as to the general case of collision, i.e. translatory
motion is converted into vibratoi^y motion, and then reconverted into
translatory motion.

The difference in the effect is, therefore, merely one of degree,
not of kind. Thus, for example, if we suppose the case of two
billiard-balls which come into collision at an ordinary speed, then
translatory motion is converted into vibratory n^otion (heat), and
then reconverted into translatory motion; the feeble vibratory
motion developed being merely sufficient to cause a slight reces-
sion of the molecules without separating ; but if we suppose the
balls to come together at a cosmical speed (say at fifty miles a
second), the vibratory motion developed would at its conversion
into translatory motion cause the rebound of the integral molecules
of the balls in the form of dissociated vapour at the temperature
of flame.

It may be observed, that on account of the possible long con*
tinuance of the propulsive action in the case of gravity, the final
speeds attained may be very much greater than in the case of
chemical action, so that by the approach of matter under the
action of gravity, the vibratory motion developed may be such,
that at its conversion into translatory motion, the chemical ele-
ments of the entire quantity of matter may be dissociated.

183. Taking, therefore, the case of a quantity of matter which
has approached a common centre at a high speed under the action
of gravity, then the whole body of matter would after the collision
be propelled backwards to a considerable distance by the expan-

jsjve action of the translatory motion of its component molecules.

125

the whole quantity of matter expanding over a large radial area
in the form of a nebulous mass of incandescent vapour.

Since this expansion can only take place in direct opposition
to gravity, part of the translatory motion of the gaseous molecules
would be thereby expended on the ether in overcoming the action
of gravity ; and since this translatory motion is derived from and
sustained by the vibratory motion, the conversion of vibratory
motion into translatory motion at the expansion of the vaporous
mass would be attended by a large expenditure of vibratory
motion (a large absorption of heat). The heat would thus be
greatly moderated by the extensive expansion taking place.

These physical conditions would be specially adapted for the
eventual development of a large supply of heat, in the subsequent
extensive contraction of the nebulous mass under the action of
gravity as the cooling down proceeds, and also by the eventual
combination and subsequent gradual approach of the molecules
of the dissociated elements as the temperature decreases.

The more intense the development of heat, the more rapid is
necessarily its dissipation in the surrounding ether. The above
train of physical causation would, therefore, have the effect of pre-
venting the extremely rapid dissipation of heat that would occur
were the entire energy of the approach allowed to remain in the
form of heat. But in the actual fact the intense initial heat lasts
but an infinitesimal instant of time, a great part of the heat being
instantly converted into translatory motion at the rebound of the
molecules and the attendant extensive expansion of the vaporous
mass ; the development of heat being thereby moderated, and at
the same time a train of physical conditions is prepared such
that an eventual slow development of heat takes place, whereby a
supply of heat becomes available for a long subsequent period.

184. It is a generally admitted point that the sun is losing a
greater amount of energy in the form of heat than is being sup-
plied. But is the cooling down of the sun and other stellar suns
of the universe into inactive masses of cold dead matter to be the
final end ? We may observe here, in connection with this subject,
that the deductions to which we have been led, on necessary
theoretic grounds, relative io the weakening of the molecular
actions generally, or the weakening of the action of the ether
upon molecules, attendant on a reduction of the vibrating energy
of the molecules (reduction of temperature), would appear to
have a direct bearing on this subject ; for the working of physical
phenomena, consisting fundamentally in movements of approach
and recession, and a recession being absolutely necessary to a
second approach; this weakening of the molecular action at-
tendant on a reduction of vibrating energy would be the physical
condition required for that reversal of the physical process which
is absolutely essential to its repetition, or to the continued working
of physical phenomena, the reversal being the condition required

120

for the continued action of the ether in recurring cyclical pro-
cesses, as consistent with the perpetuity of natural phenomena or
the continuance of physical change in the universe ; otherwise, the
final end of all change and activity in the universe in one uniform
state of useless inaction would be the inevitable result of natural
causation.

It may, therefore, be observed here, as having a special bearing
on this subject, that the theory of " potential enerory " and
" action at a distance " would necessarily involve the assumption
that natural causation is so constituted as eventually to bring the
entire universe to a standstill or deadlock : moreover, it may be
observed that this theory would also necessarily involve the
assumption that, in order for the present state of things to have
been brought about, a complete revulsion in the recognized work-
ing of natural causation would be required.

185. We cannot avoid the conclusion that there is even direct
physical evidence of this disintegration of matter effecting itself
at a low temperature, if we truly interpret the meaning of the
vast quantities of subdivided and scattered material which per-
vades space in the form of meteoric matter, as dust, &c., and
which it is necessary to conclude must pervade space in every
direction, since this disintegrated matter has been actually traced
to the paths of comets, which class of bodies is known to pervade
space in every possible direction.

That the existence of this vast quantity of disintegrated matter
must have a purpose and a most important part to play in phy-
sical phenomena must be at once evident. The number of meteor
systems contained even within the limited range of the solar
system is considered on valid grounds to amount to millions, even
the narrow track of the earth being known to pass through hun-
dreds of these systems. What must, therefore, be the fact if we
regard the vast volume of space separating the stellar suns?
What could be the origin or purpose of this vast quantity of. dis-
integrated matter if this be not the disintegrated material of
former suns on its course towards the formation of new suns, or
rather nebulas ? If we were to give an opinion on this question, we
should be led, on theoretic grounds, to infer that the order of the
great cyclical chain of phenomena was: Nebula — Sun — Meteoric
matter — Nebula; and that in the present day we have physical
phenomena in all these stages, the present being in this respect a
type of the past, and that although continual change is going on,
and there may be no actual repetition as regards distribution and
quantity of matter, still the changes of the universe take place in
one fundamental order of succession, in recurring cyclical pro-
cesses, as consistent with the perpetuity of natural phenomena,
and the continuance of physical change and activity in the
universe.

127

SECTION XXV.

THE ELECTRIC PHENOMENA.

186. Before proceeding to touch upon the effects comprised as
the "electric" phenomena, we will in the first place consider
briefly the production of motion at a distance, or the transmission
of signals as a mechanical problem. Firstly, we may note that
there are two possible methods of producing motion at a distance :
the one consisting in the transmission of matter across the inter-
veniug space to the object to which it is desired to communicate
motion; the second method consisting in the transmission of
motion (in the form of an impulse or wave) along a train of matter
which exists in the intervening space between the object to which
it is intended to impart motion.

The first of these methods is evidently but a clumsy mecha-
nical device ; for to maintain an entire train of matter in motion
at once, or to transmit continuously a stream of matter across the
intervening space in order to communicate motion to an object,
would especially be ill adapted to long distances ; the maintenance
of the train of matter itsielf in motion requiring perhaps as much
work as the movement of the object.

On the other hand, by the second method there is no actual
transmission of matter, and therefore the resistance due to the
bodily propulsion of a train of matter across the intervening space
is entirely avoided; there being also other special mechanical
advantages in the method of producing motion at a distance by
waves, which we shall have occasion to refer to.

187. The action of the apparatus known as the "pneumatic
bell " may serve as a practical illustration of this latter method.
The arrangement consists essentially, as is known, of a tube con-
taining air, along which a wave is transmitted, due to any disturb-
ance produced at one end of the enclosed column of air, by which
means the motion serving as a signal is produced at the farther
Qnd of the air column.

Eegarding the mechanism of the arrangement, we have here
in the form of the air column enclosed within the tube a train of
matter consisting of small masses (the molecules of air), among
which a rapid ii^terchange of motion is continually going on, so
that it becomes only necessary to disturb in any way the motion
of these small masses at one extremity of the tube, when by a
self-acting mechanism the disturbance is propagated with rapidity
to the opposite extremity, the small masses simply exchanging
motion and propagating the signal at their own normal velocity.

Here we have the best conceivable mechanical arrangemevil

128

for the transmission of signals ; indeed, it may be said that if one
were to attempt d priori as a mechanical problem to scheme out
the best or simplest conceivable device for the transmission of
signals, the prmciple involved in this mechanism of the air
column would constitute the only true solution to the problem.

188. In principle, the conditions required to satisfy the pro-
blem evidently are, first, to have a train of matter in rapid and
continuous motion, so as to be disposable at any time to transmit
a signal at a high speed, without the necessity for imparting to
the train of matter the motion by means of which it transmits
the disturbance producing the signal. Secondly, in order that
this train of matter may be always at disposal, it is necessary that
the motion of the parts of the train should take place in such a
way that the train of matter, as a whole, preserves a fixed position,
and is maintained in equilibrium. Thirdly, in order to render a
high speed practicable without disturbing eflTects, the moving
masses must be small, so that each by itself is incapable of pro-
ducing disturbing efiects.

These are precisely the mechanical conditions fulfilled in the
simplest conceivable manner in the case of the air column by
which the signal of the pneumatic bell is transmitted. In order
to transmit a signal, it is only necessary to disturb, i. e. to increase
or diminish, the normal velocities of the air molecules at one end
of the column by an amount however small, when the disturbance
is transmitted automatically, at the normal speed of the air mole-
cules, to the farther end of the column.

If the column consisted of hydrogen gas, the normal speed of
whose molecules exceeds by about four times that of the molecules
of air, it would be possible to transmit a signal at about four times
the speed.

It serves well to show the incomparable superiority of the
method of transmitting signals by waves as contrasted \n ith the
clumsy device of transmitting a stream of matter, when it is
considered that in order to produce a signal at the velocity of
an air wave by the transmission of matter, it would be necessary
to propel the stream of matter through the tube at the speed of
a bullet. The friction and resistance in such a case may be well
imagined.

189. Since the mechanism of the air column in the tube of
the pneumatic bell is a type of the external air, the same con-
siderations equally apply here, and would therefore indicate the
admirable adaptability of the air as a mechanism for the transmis-
sion of motion to a distance, or as a means of intercommunication,
as illustrated, for example, in the case of those waves of special
periods which, by the motion transmitted to the auditory nerve,
produce the sensation of sound: the same considerations also
applying to the perfectly analogous mechanism of the ether as

concerned in the phenomena of light.

129

It would surely be difficult to imagine a more admirable or
sensitive mechanism than the molecules of air impinging against
a musical string, ready to take up every gradation of movement
of the string and transmit it to the auditory nerve, the slightest
movement of the string affecting the normal velocities of tne air
molecules, which automatically exchanging velocities transmit the
motion to a distiince, the air in its physical constitution forming a
mechanism of extreme delicacy and precision, and of the simplest
conceivMe character ; and just as the molecules of air impinging
against a musical string constitute the simplest and best-adapted
mechanism for taking up every movement of the string, and trans-
mitting it by interchange of motion to the auditory nerve, so the
smaller scale but perfectly analogous mechanism of the ether con-
stitutes the simplest and best-adapted mechanism for taking up
everjr movement of the smaller scale masses (molecules), and trans-
mitting it to the visual nerve.

The fact of the mechanism of the ether and air being the
simplest concetvahle, and the consequent similarity of the mechanism
in both cases, therefore constitutes an illustration of the mecha-
nical principle that to produce complex effects with precision and
accuracy the mechanism concerned miist be simple ; the wonderful
complexity of the phenomena of sound and colour rendering it
equally indispensable in both cases that the mechanism producing
these effects should be of the simplest character, without which
precision and accuracy in the transmission of the motions would
be impossible.

190. Turning now to the consideration of the electric phe-
nomena, and taking the observed fact that a signal can be
transmitted through a wire at about the speed of light, we have
to inquire as to the possible physical processes by which such a
result can be attained. There exist in principle but two con-
ceivable methods: first, the propulsion of a stream of matter
through the molecular interstices of the wire at the observed
speed ; secondly, the transmission of an impulse or wave along the
wire. The first method in this case will scarcely bear a serious
consideration, for even if it were conceded that a sufficiently
distinct idea could be formed of the nature of so-called " fluids "
to warrant the hypothesis of their existence, the idea of propelling
bodily a stream of fluid some thousands of miles in length, at
about the speed of light, through a wire with open lateral spaces
between the molecules, cannot but be regarded as unmechanical in
the extreme ; indeed, the idea would have some resemblance to an
attempt to force water through a pipe with sides of open network.
We do not imagine that the fluid hypothesis is at all seriously
entertained, the term " electric fluid ' being perhaps rather used
as a convenience than anything else. The fact of the appreciably
uniform rate of transmission of electricity, whether great or small
force be employed, itself is sufficient to prove that it is not a fiv/ii

i

130

which is transmitted ; for if anything were propelled through the
wire, the rate of passage woula depend on the propulsive power
employed, and it would be wholly unaccountable that the rate of
transmission should be always about equal to that of light,
independent of the will of the operator. If, therefore, nothing be
propelled through the wire, then the signal can be only transmitted
by something already in the wire, in the form of an impulse or
wave. It may also be noted that this appreciably uniform rate of
transmission, independently of the force used, is one of the known
and essential characteristics of a toave motion.

191. Regarding the structure of the wire, we have a series of
molecules at certain distances apart, maintained in positions of
stable equilibrium under the action of the ether which surrounds
the molecules and pervades the molecular interstices of the wire,
the ether within the wire forming an unbroken train of matter,
since the molecular interstices necessarily communicate with each
other.

There exist, therefore, two possible modes by which a wave can
be transmitted along the wire, viz. either by the ether indepen-
dently, or by the ether and the molecules conjointly ; for since the
molecules are separated by the ether, it would be impossible for
the molecules themselves to transmit a wave independently, i. e.
without the participation of the ether.

Now, on considering the question, it becomes tolerably apparent
that the transmission of the wave by the molecules and the ether
conjointly, involving as it does a continual change of motion
between dense and light masses, would be far too slow for the speed
of electricity. If the molecules at one end of a wire be disturbed
from their positions in any way, then this movement produces a
change of the ether pressure upon the adjacent molecules, which
causes their movement, and thus a wave is transmitted along the
wire at a certain rate dependent on the promptitude with which
the disturbed molecules recover their positions of equilibrium,
which varies with different substances, the velocity of this species
of wave transmitted by the molecules and the ether conjointly,
being given by the velocity with which the substance transmits a
wave of sound. Since, however, the velocity of transmission of such
waves will not bear comparison with the speed of electricity, we
are bound to reject the assumption that the molecules are
concerned in the transmission of the waves producing the electric
effects, and we are therefore reduced to the one remaining possible
solution to the problem, viz. that the wave is transmitted by the
ether independently.

192. It may also be observed that the velocity of transmission
of a wave propagated by the molecules of a substance would
necessarily depend on the molecular structure of the substance,
the velocity varying considerably with different substances ;

whereas this has not been observed to be the fact in the case of

131

electricity ; indeed, the appreciably uniform rate of transmission of
electricity in materials of the ffreatest diversity would by itself
warrant the inference that something independent of the materials
themselves, but present in all, would be the agent concerned in
the transmission of electricity. The ether would satisfy this con-
dition, and it may be observed, lastly, that the etlier alone (as
indicated by the speed with which it transmits a wave of lignt)
possesses in the normal motion of its particles a velocity at all
adequate to propagate, by interchange of motion, a small disturbing
effect to a distance with the speed of electricity.

193. As regards the mode of transmission of the waves pro-
ducing the electric effects, precisely the same considerations in
principle apply as in the case of the air column of the pneumatic
bell, only the particles of matter in the form of ether have a very
much higher normal velocity, the train of ether in a metallic wire
forming an analogous, beautiful, self-acting mechanism for the
transmission of signals, it being only necessary to disturb in any
way this moving train of matter at one extremity of the wire,
when the disturbance is propagated in the form of a wave to the
opposite extremity. The mechanism is automatic and of the
simplest conceivable character, the wave being propagated simply
by the re-establishment of the equilibrium of motion along the
circuit.

At the same time the system of waves or impulses forms the
suitable mechanical adaptation for producing by vibration that
disturbance or change in the ether pressure about the apparatus
employed, by which the various motions forming signals are
produced.

194. Continuous motion of some kind constitutes the only
possible physical means by which a disturbance or change of the
ether pressure can be permanently maintained; for since the
ether penetrates freely the molecular interstices of matter, it
becomes impossible to maintain a permanent change of pressure
by using matter as a barrier to exclude the ether, as can be done
in the case of the air (by the evacuation of air) ; so that continuous
motion alone (i. e. the motion of a mass or molecule of matter, or
of a portion oi the ether itself), by affecting the velocities of the
ether particles, and thereby excluding the ether by rarefying it,
can produce a permanent change of the ether pressure.

It will become evident, on considering the question, that a
vibratory form of motion is the only form of motion mechanically
adapted to this purpose; for since the disturbance or change of
the ether pressure is maintained at a fixed spot, the moving mass,
therefore, which produces the disturbance must have such a form
of motion that it can maintain a fixed position and yet disturb the
ether. For reasons already indicated, a vibratory form of motion
is in principle the only form of motion adapted to satisfy these
conditions ; for by this form of motion, the moving mass of matter

132

or ether can maintain a fixed position by oscillating about it, and
yet can disturb the surrounding ether and produce a change of
pressure.

195. The aboYe considerations as to the mode of transmission
of electricity may serve to remove any difficulty that might have
existed in appreciating how an electric signal can be transmitted
at such an immense speed with the feeble means employed, the
real state of the case being that the velocity of transmission is not
generated at all, but exists aJready; it being only necessary to
change (increase or diminish), by an amount however small, the
normal velocities of the ether particles at any point of the circuit,
when the disturbance is propagated by the simple re-establishment
of equilibrium along the whole length of the circuit, and thus by
the feeble disturbance produced by a drop of acid, a signal may
be sent thousands of miles with the velocity of light.

It appears a reasonable conclusion that the velocity of trans-
mission of the wave might be affected to a certain, relatively
small, extent by the presence of the molecules of the circuit, the
wave probably undergoing inflection; also, it may be observed
that the normal velocity of the ether particles upon which the
velocity of transmission directly depends, is affected to a certain,
relatively small, extent by the vibrations of the molecules.

APPENDIX.

Being obliged to conclude here, for the present, we will merely give a
short summary of conclusions regarding certain fundamental points, to
which we have been led as the natural deductions resulting from the
previous inferences regarding the part played by the ether in physical
phenomena, reserving a more detailed consideration of the subject to a
future opportunity.

Firstly, when an electric circuit is interrupted the waves are reflected,
necessarily producing stationary waves. " Static " electricity, or the
" static " electric state, therefore consists in stationary vibrations of the
ether in the interior of a body when said to be " charged," these vibra-
tions also disturbing the external ether and producing the phenomena of
" attraction " and " repulsion " characteristic of vibratory motions.

Since, also, the ether within a mass of matter or " conductor " is freely
movable, the plane of the waves can therefore shift itself. Thus, when a
charged metallic sphere is surrounded concentrically by matter, such as
by the appreciably uniform distance of the walls of a room, then the
waves are also concentric, and radiate in stationary vibrations on all sides.
But when a plane metallic surface is approached near the charged sphere,
then the stationary vibrations are necessarily intensified by reflection
between the two, the conditions of equilibrium causing the plane of the
waves to swing round and become parallel to the plane surface; the
lateral energy of the waves is therefore taken off, and concentrated be-
tween the opposed surfaces, the sphere accordingly now only appearing
" charged " on that side where the plane is situated.

The special action of points will be clear when it is considered that
a mass of aeriform matter in stationary vibration tends to expand in every
direction, and would therefore act with special energy along a point when
a point is fixed to a charged conductor.

It is evident that friction or any molecular disturbance whatever
would naturally throw the ether within a mass of matter into vibration.
The stationary vibration of a mass of ether has its analogy in the sta-
tionary vibration — " resonance " — of a mass of air, produced by friction,
&c. The change of " static " electricity into " dynamic " electricity, or
the '^ static " state into the '^ dynamic " state, and conversely, is simply
the change of st€Uionary vibrations into progressive vibrations, the one of
these being necessarily always capable of producing the other.

The '* magnetic " condition consists in the disturbance or wave move-
ment necess^ily produced outside a circuit, such as a wire— due to the
communication existing between the ether within the wire and the ex-
ternal ether — when a wave is transmitted through the wire.

134

It is a known and remarkable fact that the electric energy within a
circuit is the same at all points, however far from or close to the source
of energy, and however diverse the materials may be of which the circuit is
composed ; this fact possibly having led to the idea of its being a current.

This uniformity in the energy in all parts of the circuit, and also the
necessity for having a circuity is explained by the fact that the vibrations
of the ether outside the wire or circuit can only be in equilibrium among
themselves, and, indeed, can only exist when llie circuit is complete, and
thus the oscillating masses of ether can abut against each other and be in
equilibrium of pressure ; just as the component stones of an arch can only
be in equilibrium when there is a keystone, or when the circuit is complete.
Indeed, the closed or complete circuit is one of the conditions for the
existence of stationary vibrations in a medium without masses of matter
for these vibrations to abut against, the vibrations abutting against them-
selves in a complete circuit.

The stationary vibrations of the ether between two molecules of matter
exist without a complete circuit, from the fact that these vibrations can
abut against the molecules; but when matter is wanting altogether in the
line of the vibrations, then these vibrations can only exist by abutting
against themselves, which is only possible in a complete circuit ; and
the condition for equilibrium of pressure requires that the energy of the
vibrations should be perfectly uniform in all parts or throughout the
circuit. Indeed, this uniformity is necessarily self-adjusting.

Since, therefore, the vibrations outside the circuit or wire (the mag-
netic vibrations) are necessarily connected with and dependent on the
vibrations inside the wire, the one reacting upon and influencing the
other ; accordingly, therefore, the uniformity in the vibrations outside
the wire is necessanly followed by uniformity inside, whatever the nature
of the different materials forming the circuit. Thus when, for example
(without interrupting the circuit), an additional length of wire or re-
sistance is brought into the circuit, the energy of the internal (electric)
waves first falls at or near this point of the circuit, and thus the equili-
brium of motion between the internal (electric) vibrations and the con-
nected external (magnetic) vibrations is upset at this point of the circuit,
and in the readjustment of equilibrium, therefore, motion is transferred
from the stronger external vibrations to the weaker internal. The energy
of the external (magnetic) vibrations, accordingly, next falls at this point
of the circuit, and immediately in the self-acting readjustment of the
equilibrium of motion among the external vibrations, a magnetic wave
rolls round the circuit, readjusting the uniformity of wave motion out-
side (i. e. the magnetic vibrations), and with it the uniformity of the
connected wave motion inside (i. e. the electric vibrations). Thus the
conditions for equilibrium require that the electric wave motion should
be uniform throughout the circuit, and the magnetic vibrations cannot
exist at all without a complete circuit.

The electric spark is due to the disturbance produced in the ether,
attendant on the sudden change of stationary vibrations of the ether into
progressive vibrations, by which the molecules of air are displaced and
shaken into vibration, emitting light. It may be observed, that one of
the characteristics of a stationary vibration of matter is that the effects
are perfectly balanced, or the oscillating segments into which an aeriform
medium in station&rj vibration is broken up, impinge against each other

135

and balance each other's effects, the nodes or points of no motion re-
maining stationary. But when from any disturbing cause the equi-
librium of the vibratory movement of the medium is upset at any one
point, and the vibrations consequently become progressive, then the eflfects
are no longer balanced, the nodes shift their positions, and the molecules
of matter immersed in the ether may be met on one side by a condensa-
tion, on the other by a rarefaction, as the wave passes, and thus the mole-
cules may be displaced or driven out of their positions. Thus, in the
powerful eflfects of lightning, for example, the sudden change from sta-
tionary to forcible progressive vibrations of the ether within a mass of
rock may be sufficient to disintegrate it completely, or to shatter it to
fragments.

When the human system is connected to the charged conductor of an
electric machine, the stationary vibrations produced in the ether within
the system are unfelt, but when by. touching some external object (con-
necting to earth), the vibrations suddenly become progressive, a tremor
is felt, or the molecules of the system are shaken, and with a sufl&cient
power may be displaced with injurious eflfects. It would be difl&cult to
imagine a more searching or eflfective means of disturbing the molecules
or integral parts of a mass of matter than by disturbing the ether which
pervades the mass ; indeed, one might infer a priori that this would be
one of the most effective means of producing powerful dynamic effects.
The remarkable character of the effects of lightning, by which the most
rigid structures are overthrown and solid masonry shattered to frag-
ments, is in perfect mechanical harmony with the special nature of the
physical cause concerned ; a powerful pulse down tiie ether which per-
vades a tree, for example, being sufficient to split it into fibres. Indeed,
the observed effect is precisely what might be expected from the nature
of the physical cause, the disturbance of the ether which pervades matter
to the core, scattering the integral parts in all directions, and at the same
time nothing could point more unmistakably to the existence of a
powerful dynamic agent — by the disturbance of whose equilibrium these
effects are produced — than the observed remarkable dynamic effects of
lightning.

Eegarding " conductors " and " non-conductors," a " conductor " may
be defined as a body whose molecular structure is such that its molecules
are least affected by the passage of the electric waves, while a '* non-
conductor," or bad conductor, partly takes up the motion of, and partly
reflects the waves. It is obviously merely a question of degree, not of
kind ; for the molecules of all substances whatever take up the vibratory
movement of the waves to a certain degree, or all substances are heated
by the passage of electricity, and those which are heated least, or those
substances whose molecules take up the motion of the waves least, are
the best " conductors," conducting power being inversely as the heat
developed. A forcible wave movement of the enclosed ether may be
suf&cient to raise the vibratory motion of the molecules until they lose
their positions of stable equilibrium, and by their vibrations break up
the ether into waves of light, as illustrated, for example, by the fusion of
an iron wire by the passage of powerful electric waves. The attendant
disintegrating action of the wave motion is illustrated by the observed
distortion of shape and occasional scattering of the parts of an iron wire
at the point of fusion.

136

The electric phenomena being due to a wave motion of the ether, ik
wonld be a thing to be expected beforehand that any disturbanbe of tlis
molecules of substances, or any molecular disturbejice whateyer, wodd
be attended by the development of electricity, as is known to be the £ui
The energetic molecular disturbance of chemical action, by which the
molecules are driven out of their positions, would naturally be one of iha
most effective means of disturbing the ether and giving rise to the electrio
waves, the feebler disturbing action of heat and friction producing liks
but feebler effects.

Note belativb to the Pboduction of Motion thbouqh Vibration.

Id regard to the phenomena of attraction produced through vibration, we hft?e
found it a simple and effective method for illustrating the results, to float the massM
acted upon on the surface of water. Thus the simplest method is to take a smaJl
piece of cork and insert a narrow strip of card into a slit made in the cork, ti^e ocsk
Doing then placed on the surface of water, so that the strip of card is verticaL If a
tuning-fork be then struck a sharp blow and approached to the card, the latter is
distinctly attracted, and may even be made to turn round by holding the prong near
the edge of the card and turning the fork round in a circle. The effect is much greater
in close proximity, to the card. To show the marked character of the effect, the fork
may be Iield near the card, and on the latter receiving an impulse towards the
prong, if then the fork (still vibrating) be suddenly brought round to the opposite
side of the card, the ndovement due to the first impulse is checked and changed into
a movement in the opposite direction. Another experiment consists in taking
a short strip of tissue paper and placing it upon a table, when by holding tlie
vibrating prong about an eighth of an inch above the strip of paper, the latter will
spring up und adhere to the prong — a film of air being intercepted between the two
— the paper dropping off when the vibration ceases. The effect here reminds one <rf
the attraction of light substances by a rubbed piece of sealing-wax.

LOMI'OS : PBINTKD BT WILLIAM CLOWES AKD SONB, STAMFORD STREET AlID OBABXSQ CB06S.

//;' -^

* -